A "closed form expression" is any representation of a mathematical expression in terms of "known" functions, "known" usually being replaced with "elementary".

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13
votes
1answer
169 views

Closed form for $_2F_1\left(\frac12,\frac23;\,\frac32;\,\frac{8\,\sqrt{11}\,i-5}{27}\right)$

I'm trying to find a closed form (in terms of simpler functions) for the following hypergeometric function with a complex argument: ...
0
votes
0answers
68 views

Proof of a striking identity of Tito Piezas III

In the q series blog of Tito Piezas here . He gives a very striking relation I am wondering on how to prove that ?
5
votes
1answer
52 views

Closed form for derivative $\frac{d}{d\beta}\,{_2F_1}\left(\frac13,\,\beta;\,\frac43;\,\frac89\right)\Big|_{\beta=\frac56}$

As far as I know, there is no general way to evaluate derivatives of hypergeometric functions with respect to their parameters in a closed form, but for some particular cases it may be possible. I am ...
2
votes
0answers
73 views

Is there a closed form for $\Gamma(i)$?

I know that $$\Gamma(z)\cdot\Gamma(z^*)=|\Gamma(z)|^2\tag{1}$$ and $$\Gamma (z)\cdot \Gamma (1-z) =\frac{\pi }{\sin{\pi z}}\tag{2}$$ but I still can't find closed form for $\Gamma(i)$
3
votes
0answers
36 views

Solving equation with LambertW function?

Does the equation $$ a = b x e^x + c x + d e^x $$ have a solution form solution? I tried to look for it by using the LambertW funcion, but I did not succeed. Thanks in advance.
1
vote
2answers
67 views

How to find a closed form for the derivatives of $F(x)=\frac1x\int_0^x\frac{1-\cos t}{t^2}\,dt,$ $F(0)=\frac12$?

I have been given the function $$F(x)=\frac1x\int_0^x\frac{1-\cos t}{t^2}\,{\rm d}t$$ for $x\ne 0,$ $F(0)=\frac12,$ and charged with finding a Taylor polynomial for $F(x)$ differing from $F$ by no ...
1
vote
1answer
118 views

How to prove that $\sum_{n=1}^{+\infty}\frac{1}{n^2+1}=\frac{-1+\pi \coth (\pi)}{2}$?

I typed into my Mathematica:$\sum _{n=1}^{\infty } \frac{1}{n^2+1}$ , and the result was: $$\frac{-1+\pi \coth (\pi)}{2}$$ I know how to estimate the aforementioned sum , but I have no idea how to get ...
0
votes
0answers
29 views

Help with formulating a mathematical logic formula

I need to write a precise mathematical expression to formulate an algorithm that could be implemented in software. It has the following simple logic: An Internet user of the software in a ...
0
votes
1answer
18 views

Is there a closed form solution for the motion of a particle with friction?

I am trying to find a solution to Newton's equation of motion $ \boldsymbol{F} = m \boldsymbol{\ddot{r}} $ assuming a constant force $ \boldsymbol{F} $ but accounting for kinetic friction which is a ...
1
vote
1answer
20 views

Close formula for the following iterative process

I'm trying to get a formula which results in the number of merge steps needed to merge several intermediate files. The code comments which I'm studying say: ...
3
votes
2answers
108 views

Finding the closed form of a sum

I would like to find the closed form of the sum $\sum_{n = 4}^{x}(x - n)$. I believe that the derivative is $x - 4$, but when I take the integral of that and graph it, the sum and $\frac{x^2}{2} + 4x$ ...
0
votes
1answer
54 views

Closed form of $n!\sum_{k=3}^{n-1}{{n-2}\choose{k-1}}$

$n$ is given, and it takes part in the following formula. $$n!\sum_{k=3}^{n-1}{{n-2}\choose{k-1}}$$ Is there a nicer way for expressing it? Without the summation sign?
1
vote
0answers
42 views

Closed form double integral $ \int_{a}^{c}dr \int_{b}^{d} dr' \, \frac{r r'}{\sqrt{(r - a)(r' - b)(r-c)(r'-d)}} \frac{r_<^{\ell}}{r_>^{\ell+1}}$

Is there a closed form expression for $$ S_\ell = \int\limits_{a}^{c}dr \int\limits_{b}^{d} dr' \, \frac{r r'}{\sqrt{(r - a)(r' - b)(r-c)(r'-d)}} \frac{[\min( r , r')]^{\ell}}{[\max(r,r')]^{\ell+1}} ...
5
votes
2answers
249 views

Closed form integral $\int_b^c \frac{x^2}{\sqrt{(x-a)(x-b)(c-x)(d-x)}} dx$

Is there a closed form expression for the definite integral $$I=\int_b^c \frac{x^2}{\sqrt{(x-a)(x-b)(c-x)(d-x)}} dx$$ for $a<b<c<d$? Mathematica 9.0 can do it for special cases using ...
2
votes
1answer
66 views

Closed form expression for series of a 3rd order reccurrence, repeated roots

For the series: 1,1,2,3,4,6,9,13... The rule is: F(n+3)=F(n+2)+F(n) with starting conditions F(0)=F(1)=F(2)=1. I found a closed form expression using a variation on a matrix based proof used for the ...
7
votes
2answers
105 views

What is the mathematical relevance of whether an expression has a closed form?

In the evaluation of mathematical expressions, particularly integrals, I often find a statement that the expression has or does not have a closed form. I looked up the definition, and the important ...
0
votes
0answers
44 views

Can the method of generating functions be applied to linear recursions of order $>4$?

I just got in touch with the method of solving recursions with generating functions. However, even if it is not mentioned anywhere, it seems to me, this approach is not applicable for recursions of ...
0
votes
1answer
48 views

Can every recurrence relation be solved?

Motivation A possible way to solve an ODE is to express the solution as: $y= \sum_{n=0}^\infty a_nx^n$. We substitute in the ODE and then calculate the coefficients $a_n$. For example, $y''+y=0$ ...
8
votes
3answers
215 views

Evaluating $\int_0^1 \frac{\text{Li}_2 \left(-\frac{1}{1-z}\right)-\text{Li}_2 \left(-\frac{1}{1+z}\right)}{z}dz$

I was trying to find a closed form for $$\int_0^1 \frac{\text{Li}_2 \left(-\frac{1}{1-z}\right)-\text{Li}_2 \left(-\frac{1}{1+z}\right)}{z}dz = -2.454199511\cdots$$ where $\text{Li}_2(z)$ is the ...
2
votes
3answers
64 views

Closed form for a trigonometric partial sum

I know that: $$\sum_{k=1}^n\arctan(2k^2)=\frac{\pi n}{2}-\frac{1}{2}\arctan(\frac{2n(n+1)}{2n+1})$$ Can a similar closed form expressions be given for $\sum_{k=1}^n \arctan(k^2)$? I was able to ...
2
votes
1answer
192 views

Integrating a complicated function

After spending a couple of weeks, I was able to find the solution to a certain differential equation, given below (Well they are the eigenfunctions to be exact): $$y_n(x) = ...
1
vote
1answer
123 views

Closed form for $\sum_{k=1}^{\infty} \zeta(2k)-\zeta(2k+1)$

From WolframAlpha it seems that $$ \frac{1}{2}=\sum_{k=1}^{\infty} \zeta(2k)-\zeta(2k+1) $$ Could someone provide a proof for this? Thanks.
1
vote
1answer
35 views

Determinant of parametric function and $0!1!2!…n!$

As answer to this question, I trued to calculate the wronskian of: $$\left| \begin{array}{ccc} e^x & e^{2x} & ... & e^{nx}\\ e^x & 2e^{2x} & ...& ne^{nx} \\ e^x & 4e^{2x} ...
2
votes
3answers
79 views

I flip M coins, my opponent flips N coins. Who has more heads wins. Is there a closed form for probability?

In this game, I flip M fair coins and my opponent flips N coins. If I get more heads from my coins than my opponent, I win, otherwise I lose. I wish to know the probability that I win the game. I ...
2
votes
1answer
57 views

Generating function of $ \lim_{x\rightarrow 0} \frac{1}{n!} \frac{\partial^n}{\partial x^n} [(1+ax)^n f(x)] $

Is there a closed form for the generating function (or exponential generating function) of the sequence $$s_n= \lim_{x\rightarrow 0}\frac{1}{n!} \frac{\partial^n}{\partial x^n}\left[(1+ax)^n f(x) ...
2
votes
1answer
80 views

Evaluate $\sum_{n=1}^{\infty} \frac{\ln n}{(n+1)!}$

Is there a closed form expression for this sum (or very similar sums) with known transcendental functions or irrational numbers? $$\sum_{n=1}^{\infty} \frac{\ln n}{(n+1)!} \approx ...
0
votes
0answers
51 views

Closed Form CDF of the Variance Gamma Distribution

What is the closed form cumulative distribution function of the variance gamma distribution? The PDF is ...
0
votes
0answers
27 views

Closed form for a special recursion?

Does the recurrence relation $$ a(n+1) = a(n)^2 + 1,\quad a(1)=1, $$ have a closed form solution? I have tried hard to find it, but failed. Any ideas ? I am particular interested in prime ...
3
votes
1answer
117 views

Closed form for $\sum\limits_{k=1}^{\infty}\zeta(4k-2)-\zeta(4k)$

I am looking for a closed form of the expression $$ \sum_{k=1}^{\infty}\zeta(4k-2)-\zeta(4k) $$ Closed form would be something in terms of constants such as $\pi$, $\gamma$, $e$, etc.
0
votes
3answers
480 views

Integral $\int_{0}^{3} \frac{e^{-x^2}}{\sqrt{1-x^2}} \,dx$

I recently got stuck on evaluating the following integral, $$ \int_{0}^{3} \frac{e^{-x^2}}{\sqrt{1-x^2}} \,dx. $$ Is it possible to evaluate this integral in a closed form? I am not sure if there is ...
0
votes
0answers
26 views

Closed expression for simple recursive formula

I would like to express the following recursive formula in a closed expression. $V_\tau=(1+R)V_{\tau-1}+\tau(c-p\lambda\mu)+constant$ where: $\tau\geq1$ $V_1=\frac{1}{2}(2u+c-p\lambda\mu)R$ ...
5
votes
1answer
141 views

Evaluating $\int_0^{\frac{1}{2}}\log^2(2\sin(\pi x))\cos(\pi(1-2x))dx$ [closed]

How can we prove following formulas $$\int_0^{\frac{1}{2}}\log^2(2\sin(\pi x))\cos(\pi(1-2x))dx=\frac{-1}{4}$$ or $$\int_0^{\frac{1}{2}}\log^3(2\sin(\pi x))\cos(\pi(1-2x))dx=\frac{\pi^2+6}{16}$$
10
votes
5answers
430 views

Closed form for $\int_{0}^{1/2}\left(2x - 1\right)^{6}\ \log^{2}\left(2\sin\left(\pi x\right)\right)\,{\rm d}x$

How can I find a closed form for the following integral $$ \int_0^{1/2}\left(2x - 1\right)^{6}\ \log^{2}\left(2\sin\left(\pi x\right)\right) \,{\rm d}x $$
3
votes
1answer
171 views

Analytic solutions to $f(x+y) +h(x+y)= f(x)(g(y)+h(y)) + g(x)(f(y)+h(y)) + h(x)(f(y)+g(y))$?

Let $x,y$ be complex numbers. Consider $f(x+y) +h(x+y)= f(x)(g(y)+h(y)) + g(x)(f(y)+h(y)) + h(x)(f(y)+g(y))$ valid for all $x,y$. What are the analytic solutions for $f,g,h$ ? Can we conclude an ...
13
votes
2answers
241 views

Closed form of $\int_0^\frac{1}{2}x^n\cot(\pi x)\,dx$

What is the closed form of the following integral $$\int_0^\frac{1}{2}x^n\cot(\pi x)\,dx,n\in\mathbb{N}$$ By Mathematica I saw that $$\int_0^\frac{1}{2}x\cot(\pi x)\,dx=\frac{\log(2)}{2\pi}$$ ...
2
votes
1answer
43 views

A closed form for $\sum_{i\cdot j^k=n}(-1)^i$?

$$\alpha_k(n) \stackrel{\text{def.}}{=} \sum_{i\cdot j^k=n}(-1)^i.$$ Does a closed form exist for $\alpha_k(n)$? For low values of $k$: $$\alpha_0(n)=(-1)^n$$ $$\alpha_1(n)=\begin{cases} ...
14
votes
3answers
265 views

$\sum_{n=1}^{\infty}\frac{H_n}{n^2 2^n}=\zeta(3)-\frac{1}{2}\log(2)\zeta(2)$

How can I prove that $$\sum_{n=1}^{\infty}\frac{H_n}{n^2 2^n}=\zeta(3)-\frac{1}{2}\log(2)\zeta(2).$$ Can anyone help me please?
0
votes
0answers
57 views

Closed form for matrix multiplication

Let Q be a n by n positive definite or positive semi definite matrix and g be a vector in $R^{n}$. Is there a closed form to get x? $g^{T}Q^{k}g = x(g^{T}Qg)$ where k is a some integer number.
2
votes
2answers
164 views

Closed form expression for unusual sum of binomial coefficients

How do I get a closed form expression for $\sum_{i=c}^{n} i\binom{i}{c}$? Note that the index ranges over the upper values of the binomial, not the lower. I know computer algebra systems can give me ...
14
votes
1answer
130 views

Closed form for $\sum_{n=0}^\infty\frac{\operatorname{Li}_{1/2}\left(-2^{-2^{-n}}\right)}{\sqrt{2^n}}$

Let $$S=\sum_{n=0}^\infty\frac{\operatorname{Li}_{1/2}\left(-2^{-2^{-n}}\right)}{\sqrt{2^n}},\tag1$$ where $\operatorname{Li}_a(z)$ is the polylogarithm. For $a=1/2$ it can be represented as ...
3
votes
2answers
58 views

Does $E^2 \; ( E \approx 1.2640847\ldots)$ equal $D \approx 1.5979102\ldots$?

Does $E^2=D$? Where $E$ is a constant used in the closed form of the Sylvester Sequence (see: Closed form formula and asymptotics) and $D$ is a constant for the closed formula of the sequence A007018 ...
39
votes
2answers
395 views

Conjecture $_2F_1\left(\frac14,\frac34;\,\frac23;\,\frac13\right)=\frac1{\sqrt{\sqrt{\frac4{\sqrt{2-\sqrt[3]4}}+\sqrt[3]{4}+4}-\sqrt{2-\sqrt[3]4}-2}}$

Using a numerical search on my computer I discovered the following inequality: $$\left|\,{_2F_1}\left(\frac14,\frac34;\,\frac23;\,\frac13\right)-\rho\,\right|<10^{-20000},\tag1$$ where $\rho$ is ...
11
votes
1answer
161 views

Integral $\int_0^\infty\exp\left(-\sqrt2\,x^2\right)\,\operatorname{erfi}(x)\,\log(x)\,x^3\,dx$

Consider the following integral: $$\mathcal{A}=\int_0^\infty\exp\left(-\sqrt2\,x^2\right)\,\operatorname{erfi}(x)\,\log(x)\,x^3\,dx,\tag1$$ where $\operatorname{erfi}(x)$ denotes the imaginary error ...
1
vote
1answer
51 views

How to find algebraic simplification for recurrence relation with closed-form solution, specifically for the Lucas-Lehmer primality test

I have a question based on the section Proof of correctness in the article Lucas-Lehmer primality test, see following link. ...
17
votes
3answers
372 views

Closed form for integral $\int_{0}^{\pi} \left[1 - r \cos\left(\phi\right)\right]^{-n} \phi \,{\rm d}\phi$

Is there a closed form for $$I_n =\int_{0}^{\pi} \frac{\phi}{(1 - r \cos\phi)^n} \,{\rm d}\phi $$ for $\left\vert\,r\,\right\vert < 1$ real and $n > 0$ integer ? The solution to this integral ...
19
votes
3answers
456 views

Integral $\int_0^\infty x^2\,e^{-x^2}\operatorname{erf}(x)\,\log(x)\,dx$

I need to evaluate this integral: $$I=\int_0^\infty x^2\,e^{-x^2}\operatorname{erf}(x)\,\log(x)\,dx\tag1$$ I tried to do this in Mathematica and it returned a result of the form ...
23
votes
2answers
238 views

Need help with $\int_0^\infty e^{-x}\ln\ln\left(e^x+\sqrt{e^{2x}-1}\right)\,dx$

I need help with this integral: $$\int_0^\infty e^{-x}\ln\ln\left(e^x+\sqrt{e^{2x}-1}\right)\,dx\approx0.20597312051214...$$ Is it possible to evaluated it in a closed form?
9
votes
2answers
326 views

Integral $S_\ell(r) = \int_0^{\pi}\int_{\phi}^{\pi}\frac{(1+ r \cos \psi)^{\ell+1}}{(1+ r \cos \phi)^\ell} \rm d\psi \ \rm d\phi $

Is there a closed form for $|r|<1$ and $\ell>0$ integer? The solution for the special cases $\ell=2$ and $4$ would also be interesting if the general case is not available. Integrating ...
1
vote
3answers
190 views

Closed form for integral $ \int_0^{\pi} \frac{\sin (m \phi)}{(1 + r \cos \phi)^n} d\phi$

Is there a closed form for $n>0$ integer, $m\neq 0$ integer, and $|r|<1$ real?
17
votes
1answer
339 views

Integral $\int_0^\infty\frac{\ln\left(\sqrt{x+1\vphantom{x^0}}-1\right)\,\ln\left(\sqrt{x^{-1}+1}+1\right)}{(x+1)^{3/2}}dx$

Another integral similar to my previous question: $$\int_0^\infty\frac{\ln\left(\sqrt{x+1\vphantom{x^0}}-1\right)\,\ln\left(\sqrt{x^{-1}+1}+1\right)}{(x+1)^{3/2}}dx$$ Could you suggets how to evaluate ...