Questions regarding functions defined recursively, such as the Fibonacci sequence.

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5
votes
5answers
99 views

Recurrence of the form $2f(n) = f(n+1)+f(n-1)+3$

Can anyone suggest a shortcut to solving recurrences of the form, for example: $2f(n) = f(n+1)+f(n-1)+3$, with $f(1)=f(-1)=0$ Sure, the homogenous solution can be solved by looking at the ...
0
votes
0answers
23 views

Recurrence relation, gambling type word problem

Problem: You decide to play at a Monaco casino. Every round you put 1 million on red. There's a 18/37 chance you will win, and a 19/37 chance you will lose the million. You keep playing until you're ...
2
votes
1answer
19 views

Clarification regarding the Josephus problem in Concrete Mathematics (Knuth, et al)

In page 9 of Concrete Mathematics, regarding the Josephus Problem, they state that "each person's number has been doubled then decreased by 1". $J(2n) = 2J(n) - 1$, for $n \ge 1$ I don't quite ...
1
vote
1answer
48 views

Infinite series for recurrence

Question 1 If I define $A(z) = \sum_{n \ge 0} a_n \frac{z^n}{n!} \tag 1$ (where $a_n$ are $3\times 3$ constant matrices indexed with n), then can we re-write $\sum_{n \ge 1} a_{n-1} \frac{z^n}{n!} ...
1
vote
0answers
41 views

Recurrence relation for Binary String Question

I have a question which has been a little stumped. I'm pretty sure I know the answer, but don't know how to prove it to be true. Here it is: "Given an infinite length random binary string, what is ...
1
vote
2answers
82 views

How can i find if a given number occurs in a custom Fibonacci sequence?

Its a recent interview question from Amazon. For e.g. let starting numbers be $a$ and $b$, then third number will be $a+b$ and so on: forming recursion like: $F(n)=F(n-1)+F(n-2) , n\ge 2$ $F(1)=a$ ...
2
votes
1answer
41 views

Linear recurrence relation in Cantor-like sets

I have a linear recurrence relation $$a_i = \alpha_0 a_{i-1} + \beta(i)$$ Where $\beta(i) = \beta_0b_i$ with $b_i \in \{0,1\}^\mathbb N$ I know that $0 < \alpha_0 < \frac{1}{2}$, $\beta_0 = 1 ...
0
votes
3answers
53 views

Finding general formula for a recursion function

If we have a recursion relation defined as $a_n = 3a_{n-1}+1$ with $a_1=1$ then find the general formula for $a_n$ in terms of $n$ with a(1) = 1. So far I have: $a_n = 3a_{n-2}+1+1 = 3a_{n-3}+1+1+1 ...
0
votes
1answer
34 views

Initial values appear from nothing

This answer says that any casual sequence of the kind $y_n = y_{n-1} + y_{n-2} + y_{n-3} + \ldots $ will stay constant-0 because $y_0$ is a sum of zeroes, so is $y_1$ and the rest of the sequence. I ...
3
votes
2answers
89 views

Fibonaaci Recurrence

This is an interesting question where we are trying to solve another recursion which has same tree structure as the given recursion and also has term similarities Given Data in question ...
1
vote
1answer
43 views

Find all solutions of the recurrence relation $a_n = 5a_{n-1} - 6a_{n-2} + 2^n + 3n$

Question: Find all solutions of the recurrence relation $a_n = 5a_{n-1} - 6a_{n-2} + 2^n + 3n$ (Hint: Look for a particular solution of the form $qn2^n + p_1n + p_2$, where $q, p_1, p_2$ are ...
0
votes
0answers
24 views

Solving a simple Recurrence in summation form(very special case)

I have a bit confusing recursion form $\sum_{n=2}^{\infty}\{f(n)\frac{n}{n-1}\}=C, \tag 1$ $f(0)=b,f(1)= a,f(2)=c$ and $C$ are constants. Could you help me to solve this recursion or help me to ...
0
votes
0answers
30 views

Equality of a recurrent sequence and of a running maximum of another sequence

Let $\{a_n\}$ be a sequence of real numbers. Let $c,b$ be real constants. Define $$ L_{k,n}=\exp\left\{c\sum_{i=k}^n(a_i+b)\right\}. $$ Then it can be shown that $L_n=\max_{1\le k\le n}L_{k,n}$ is ...
4
votes
1answer
43 views

Is it possible to calculate the roots of the difference between successive terms of this polynomial series $\rm{P}_n (x)=x\rm{P}_{n-1}-r\rm{P}_{n-2}$

Consider the polynomial series defined by the following recursion formula: $$ \begin{align} &\mathrm{P}_0 = 1 \\ &\mathrm{P}_1 = x-r \\ &\mathrm{P}_n = x\mathrm{P}_{n-1} - ...
5
votes
0answers
83 views

Sum of infinite series defined recursively

Suppose $s$, $t$, and $\delta$ are constants satisfying $0<s<t<1$ and $\delta>1$. An infinite sequence $\{y_k\}_{k=1}^{\infty}$ defined as follows: The initial term, $y_1$, is the ...
-1
votes
1answer
51 views

Savings after $n$ years (using recurrence) [closed]

A person deposits Rs. $250, 000/$ in a bank in a saving bank account at a rate of $8 \%$ per annum. Let $P_n$ be the amount payable after $n$ years, set up a recurrence relation to model the problem. ...
7
votes
3answers
225 views

Solving recurrence relation: Product form

Please help in finding the solution of this recursion. $$f(n)=\frac{f(n-1) \cdot f(n-2)}{n},$$ where $ f(1)=1$ and $f(2)=2$.
-1
votes
1answer
56 views

Initial values are lost (diff eq to Transfer function)?

I read eternal Julius O. Smith III and he says that $$x_{n-m} = z^{-m}X(z)$$ Particularly, difference relation $$y_{n} = y_{n-1} + x_{n}$$ is solved by by $$Y = z^{-1}Y + X = {X \over ...
1
vote
0answers
30 views

Question about finite sums and integer recursions.

Let $n$ be a positive integer and let $g(n)$ be a given strictly increasing integer function such that $0<g(n)<n$ for all $n$. Also the sequence $ |g(n) - n|$ is unbounded as $n$ grows. Let ...
0
votes
0answers
35 views

Why does s = z+1?

What exactly is Laplace transform? motivated me to ask why unit function is 1/s by Laplace transform and 1/(1-z) by Z-transform? Both seem to be integrals of delta-pulse and secondary integration ...
3
votes
4answers
63 views

Elementary Proof of sum of alternating factorials

so I came across the rather interesting identity $$ \sum_{i = 0}^{\infty}\left[\sum_{j=0}^{i}\left[\frac{(-1)^j}{j!} \right] \prod_{j=0}^{i}\left[ (x-j)\right] \right] = x! $$ For positive integers ...
5
votes
1answer
70 views

Expressing a Recursion in terms of factorials

Given the recursion $$f(n) = nf(n-1) + (n-1)f(n-2) $$ $$f(0) = 1, f(1) = 1$$ How exactly does one express the target function? I know that $$f(n) = nf(n-1)$$ gives rise to $$f(n) = \Gamma(n+1)$$ ...
10
votes
3answers
250 views

Difficult Recurrence

I am trying to solve a Sangaku problem. The blue circles have radii one. The goal is to find the total area of all the other circles (the three sequences of circles repeat ad infinitum). I have ...
1
vote
1answer
29 views

Is it possible that a randomized recursion has a nonzero probability of either converging or diverging?

I have very little "hands-on" experience with probability, but here is my context: I was looking at the random Fibonacci sequence: $$f_0=f_1=1, f_n=f_{n-1}+Xf_{n-2}$$ where $X$ is chosen randomly ...
1
vote
0answers
31 views

Complex numbers product and ratio, prove this relation.

Define a table $T$ as follows: $$\text{If}\; n\geq k \; \text{then} \; T(n,k) = (2+3 i) \sum _{i=1}^{n-1} T(n-i,k-1)+(5+7 i) \sum _{i=1}^{n-1} T(n-i,k) \; \text{else} \; T(n,k) = 0$$ Then take rows ...
0
votes
0answers
27 views

Concrete math generalized josephus recursion understanding 1.15

I am studying through the josephus problem in concrete math , Here is the equation of binary form $$f(1) = α ;$$ $$f(2n + j) = 2f(n) + β_j ,$$ $$\text{ for } j = 0, 1 \text{ and } n \geq 1$$ this ...
1
vote
3answers
37 views

Why, intuitively, does the solution to a general linear recurrence relation make sense?

I reasoned through the solution to a differential equation, and $e^{\alpha x}$, for better or worse, seems to make sense. Each derivative sending the function to itself seems to suggest $e^{\alpha ...
4
votes
1answer
99 views

Does this sequence consist of squares of integers?

Question: let sequence $\{x_{n}\}$ such $$x_{0}=0,x_{1}=1,x_{2}=0,x_{3}=1$$ and such $$x_{n+3}=\dfrac{(n^2+n+1)(n+1)}{n}x_{n+2}+(n^2+n+1)x_{n+1}-\dfrac{n+1}{n}x_{n}$$ show that:$ ...
1
vote
1answer
38 views

Evaluation of a Hankel-like determinant

I consider the following determinant (Hankel-like?) $$ [f_1,f_2,...,f_n]:=\begin{vmatrix} f_1 & f_2 & \cdots & f_{n-1} & f_n\\ n-1 & f_1 & \cdots & f_{n-2}& f_{n-1}\\ 0 ...
3
votes
1answer
48 views

Solving a recurrence (with the form of a convolution) involving binomial coefficients

While dealing with a problem related to intersection of hyperplanes I have come across the following recurrence to obtain the values of $K_{j}$ \begin{array}{cccccccccc} 1 & = & ...
6
votes
2answers
116 views

Finding non-negative integers $m$ such that $(1 + \sqrt{-2})^m$ has real part $\pm 1$.

I believe that the integers $m$ with $(1+\sqrt{-2})^m$ having real part $\pm 1$ are $0, 1, 2$ and $5$, but I'm having trouble proving it. Write $$a_m = \Re((1+\sqrt{-2})^m) = \frac{(1 + \sqrt{-2})^m ...
0
votes
1answer
34 views

Prove that the elements of these two sequences are not null

Let $x_{n+1}=x_n+2y_n$ and $y_{n+1}=y_n-x_n$, where $x_1=1$ and $y_1=-1$. I tried proving by contradiction, I tried by induction, I got nothing. This is a question I had on an exam, I didn't manage ...
1
vote
1answer
27 views

Recurrence relation and combinatorics

I am reading p.4 of the article http://mercercountymathcircle.files.wordpress.com/2014/03/recurrence_relations.pdf which consider the following problem: Find the units digit of ...
1
vote
3answers
308 views

Homework - Resolve the recurrence relation

What's the closed formula of this recurrence relation? $$a_n = a_{n-1}+2a_{n-2}+2^n \text{ with } a_0=1, a_1=2 $$
4
votes
0answers
41 views

How to solve a non-homogeneous second-order linear difference equation with both a forward and a backward difference?

Quite a long title for this: I'm looking for the general solution of the following difference equation: $$ax_{t+1} -bx_t + x_{t-1} = c + u_t$$ where $a,b,c$ are real constants and $u_t$ is a bounded ...
1
vote
0answers
29 views

Possible to determine if a more 'compact' solution to a linear recurrence exists?

Given a linear a recurrence relation. It is possible to express a solution in terms of summations, products, and the coefficients which appear in the recurrence. For example, in the case of a single ...
0
votes
0answers
17 views

Comparing Generalized Continued Fractions

Gosper lays out a method (under Approximations) for comparing regular (a.k.a simple) continued fractions which have all partial numerators set to 1. Continue comparing terms until they differ, then ...
0
votes
1answer
67 views

Solving this recurrence relation

please tell me a way to solve this recurrence $$n\cdot R_n=C_1\cdot R_{n-1}+C_2\cdot R_{n-2}.$$ $C_1$ and $C_2$ are constants.. There is an $n$ there in the left hand side.. it makes mess. I tried ...
0
votes
0answers
59 views

solution of a recurence equation

The equation is $f(n)=\left(1+\frac{na}{b}\right)f(n-1)-\frac{na}{b}f(n-2)-\frac{n}{b}$ where $a,b>0$ and real, and $f(0)=0$, $f(1)=c\in R$. I expressed $f(2)$, $f(3)$, $f(4)$ and $f(5)$ in ...
3
votes
1answer
31 views

Newton Rhapson Algorithm Accuracy

I read somewhere that the NR algorithm in general (given an appropriate initial value) increases in accuracy by roughly two decimal places per iteration. Is this something that can be proven, or is ...
6
votes
0answers
89 views

Nonlinear inhomogeneous recurrence $f(x)^2=f(x+1)+S(x)$ to find nested radical

I want to solve the recurrence relation $$f(x)^2=f(x+1)+S(x)$$ where $S(x)$ is a given polynomial. The background is to find nested radicals expressions of the form ...
4
votes
1answer
96 views

Going from closed form to recurrence relation

If I had a closed form for a sequence that I suspect to represents a recurrence relation how would I determine the recurrence relation? In particular, I have the sequence $$a_n = ...
0
votes
1answer
36 views

Recursive Relationship: Paper Towels

A standard roll of paper towels consists of a cardboard tube with outer diameter $4$ cm. Imagine the paper being wound onto the cardboard tube. After each complete winding, the total diameter of the ...
9
votes
8answers
259 views

Proof that if $a_1=1$ and $a_{n+1}=1+\frac{1}{1+a_n}$

Question: Proof that if $$a_n=\left\{ \begin{array}{ll} a_1=1\\ a_{n+1}=1+\frac{1}{1+a_n} \end{array} \right.$$ then $a_n$ converge, and then find $\lim_{n \to \infty}a_n$. I found ...
26
votes
3answers
523 views

Finding every $n$ such that $a_n$ is an integer

Let us define $\{a_n\}$ as $a_1=a_2=1$,$$a_{n+2}=a_{n+1}+\frac{a_n}{2}\ \ (n=1,2,\cdots).$$ Then, is the following conjecture true? A conjecture : If $a_n$ is an integer, then $n\le 8$. I ...
3
votes
2answers
47 views

recurrent events-Probability of even number of successes

Let E be the event of an even number of successes. $u_n$:Probability of E occurring at the nth trial not necessarily for the first time $f_n$:Probability of E occurring at the nth trial for the first ...
0
votes
0answers
27 views

Produce a list of the most-similar units, given various correlations/relationships

I have a database full of units (U1 - U50, U51...) where every unit has the same standard attributes (A1 - A10) and where a % of each attribute defines the amount of that attribute for that particular ...
1
vote
0answers
39 views

General Solution to Linear Difference Equation: Is this correct

Notation: Let $$Q_1[f(x)] = \lim _{h \rightarrow 1} \frac{f(x + h) - f(x) }{h}$$ And let $$Q_1^{-1}\left[f(x)\right] = G(x)|Q_1\left[g(x)\right] = f(x)$$ Consider the equation $$a_0(x) + ...
2
votes
1answer
54 views

Filling of a tank - recurrence relation

Suppose a tank has a maximum limit of 100 units. Each day 2,1 and 0 units are added to the water level with probability p,r and q. Any excess water would overflow and if it reaches the minimum level ...
13
votes
4answers
354 views

Converting recursive equations into matrices

How do we convert recursive equations into matrix forms? For instance, consider this recursive equation(Fibonacci Series): $$F_n = F_{n-1} + F_{n-2}$$ And it comes out to be that the following that ...