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Oct
16
comment Is there a fast way to compute coefficient of some term of the product of some series'?
@user100508 Yes there is someting to do in that case, perhaps ask a new question for that particular case.
Oct
15
comment Is there a fast way to compute coefficient of some term of the product of some series'?
@user100508 Using $A*B$ to be the cauchy product of two series, you could derive that it is in fact a convolution. In particular, it is associative, so for $A*B*C$, start by computing $D=A*B$ and then $D*C$. I do not know of a more elegant formula other than the one you'd get arranging all the sums this process give you
Oct
15
answered Is there a fast way to compute coefficient of some term of the product of some series'?
Oct
15
reviewed No Action Needed probability without replacement and unknown number in urn
Oct
15
comment How do I reduce this: $\frac{2}{x\ln(4)}\quad ?$
don't, mostly everyone stumbles at one point or another onto something quite obvious.
Oct
15
comment Closed form for $\int_0^\infty\frac{\sqrt{x+\sqrt{x^2+1}}}{\sqrt{x\phantom{|}}\sqrt{x^2+1}}e^{-x}dx$
@user64494 What I gave above evaluates to $1.8660736602994162541590468656767972604020575060868...$
Oct
15
comment Closed form for $\int_0^\infty\frac{\sqrt{x+\sqrt{x^2+1}}}{\sqrt{x\phantom{|}}\sqrt{x^2+1}}e^{-x}dx$
Probably, Maple gives $(1/2)\pi\sqrt{2}(\sin(1/2)*BesselJ(0, 1/2)-\cos(1/2)BesselY(0, 1/2))$
Oct
15
comment Gaussian density function satisfies $y'=-xy$. Coincidence?
Have a look at digilib.lib.unipi.gr/spoudai/bitstream/spoudai/542/1/…
Oct
15
reviewed Looks OK How do I reduce this: $\frac{2}{x\ln(4)}\quad ?$
Oct
15
answered How do I reduce this: $\frac{2}{x\ln(4)}\quad ?$
Oct
15
reviewed No Action Needed If $x$ is irreducible, and $x\nmid y$, why are $x$ and $y$ relatively prime?
Oct
15
revised Prove that $6$ divides $n(n + 1)(n + 2)$
edited tags
Oct
14
reviewed Reject Question on questions in Spivak's Calculus?
Oct
14
reviewed Approve Integration by parts: $\int xe^{-x}dx$
Oct
14
revised Determine convergence $\sum_{n=1}^\infty\left(\frac{2 n + 2}{2 n + 3}\right)^{n^2}$
deleted 1 characters in body; edited title
Oct
14
comment What does $\sum_{k=1}^{\infty} \frac{4^k+5}{5^k + k}$ converge to?
T0 $100$ digits precise, it converges to $4.87153489744979239691073609504037432974495311954885531318820133050108439459357‌​2900627247672463071002$, if that sparks someone's mind. WA could not find an exact match
Oct
13
comment Coupon selecting problem
Well, it is the same distribution, with different parameter
Oct
13
revised Coupon selecting problem
added 1024 characters in body
Oct
13
answered Coupon selecting problem
Oct
12
comment Another math contest problem: $\int_0^{\frac{\ln^22}4}\,\frac{\arccos\frac{\exp\sqrt x}{\sqrt2}}{1-\exp\sqrt{4\,x}}dx$
@VladimirReshetnikov makes more sense now. I was only saying that because $1>\ln^2(2)/4.$