Jean-Sébastien
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 Oct 17 comment How find the minimum of the value of $n$ such $n^2\equiv 1\pmod{1007}$ Am i missing someting? $1$ will do Oct 16 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$even then Oct 16 comment Why do we call it a$\sigma$-algebra? In French, we even use the word "Tribu", which makes even less sense Oct 16 reviewed Looks OK Residue at$0$of$\frac{1-\cos z}{z^4}$Oct 16 reviewed Approve Fuchsian Groups: A counterexample 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