Jean-Sébastien
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 Oct16 comment Why do we call it a $\sigma$-algebra? @Did doesn't make more sense does it? unles they were auto referencing to the Bourbaki trive they are$even then Oct16 comment Why do we call it a$\sigma$-algebra? In French, we even use the word "Tribu", which makes even less sense Oct16 reviewed Looks OK Residue at$0$of$\frac{1-\cos z}{z^4}$Oct16 reviewed Approve Fuchsian Groups: A counterexample Oct16 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. Oct15 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 Oct15 answered Is there a fast way to compute coefficient of some term of the product of some series'? Oct15 reviewed No Action Needed probability without replacement and unknown number in urn Oct15 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. Oct15 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$1.8660736602994162541590468656767972604020575060868...$Oct15 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$(1/2)\pi\sqrt{2}(\sin(1/2)*BesselJ(0, 1/2)-\cos(1/2)BesselY(0, 1/2))$Oct15 comment Gaussian density function satisfies$y'=-xy$. Coincidence? Have a look at digilib.lib.unipi.gr/spoudai/bitstream/spoudai/542/1/… Oct15 reviewed Looks OK How do I reduce this:$\frac{2}{x\ln(4)}\quad ?$Oct15 answered How do I reduce this:$\frac{2}{x\ln(4)}\quad ?$Oct15 reviewed No Action Needed If$x$is irreducible, and$x\nmid y$, why are$x$and$y$relatively prime? Oct15 revised Prove that$6$divides$n(n + 1)(n + 2)$edited tags Oct14 reviewed Reject Question on questions in Spivak's Calculus? Oct14 reviewed Approve Integration by parts:$\int xe^{-x}dx$Oct14 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 Oct14 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