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 Dec 8 awarded Caucus Dec 8 comment Find value of sum of reciprocals of powers of a number @Wood or x=1 (instead of 0.5) Dec 4 comment Why is it that $f(x)$ is even if $f(-x) = f(x)$? Definitions do not require proof. It's like baptizing. I baptized myself ypercube. Therefore ypercube is me. We baptized even functions all those functions f that satisfy f(x) = f(-x) for all x that f is defined. Nov 20 comment How to find a general sum formula for the series: 5+55+555+5555+…? Shouldn't the summation be for k=0 up to n-1? Nov 12 comment Open mathematical questions for which we really, really have no idea what the answer is @pew Added the link above. But he thinks that if we find a proof, it will probably be an existentiaal one, not an actual algorithm, useful in practical applications. Nov 12 comment Open mathematical questions for which we really, really have no idea what the answer is For the record, Knuth said that he thinks P=NP is more plausible, in a recent interview: informit.com/articles/article.aspx?p=2213858 Nov 7 awarded Organizer Nov 7 comment Evaluate $\int_{-1}^{1} \exp(x+e^{x})\,dx$ You are fast ;) Nov 7 comment Subgroups of Order $p^2$ in $\mathbb{Z}_p \oplus \mathbb{Z}_p$ You already say that the order of the group is $p^2$. So you have a bag with $X=p^2$ items. You take $X$ items and put them in another bag. How many ways to do this? Nov 7 comment Examples of mathematical discoveries which were kept as a secret I'm not anything near an expert in math history but you are saying that we have no evidence of Fermat proving for example that $x^4+y^4=z^4$ has no solutions or any of the many theorems that carry his name? Nov 7 comment Examples of mathematical discoveries which were kept as a secret Very interesting! Hidden by accident. Nov 6 comment Reference request for unknown mathematical constant Using $\frac{1}{m(m+1)^2} = \frac{1}{m} - \frac{1}{m+1} - \frac{1}{(m+1)^2}$ Nov 6 comment Does the A001921 linear recurrent integer sequence always yield composite numbers? Why you considered $a(64n+17)$ and not $a(64n+33)$? Nov 6 comment Union of power sets of the counting numbers It's an infinite set that its elements are finite. Nov 6 comment Prove that $\frac{1}{a^3(b+c)}+\frac{1}{b^3(a+c)}+\frac{1}{c^3(a+b)}\ge \frac32$ How will you use the Cauchy-Schwarz? Do you mean the AM-GM inequality perhaps? Nov 6 comment Proving that $\frac{\pi ^2}{p}\neq \sum_{n=1}^{\infty }\frac{1}{a_{n}^2}$ What are the $a(n)$? Are you asking to prove that no sequence of positive integers can have this as result? Nov 6 revised does $\int_0^\infty x/(1+x^2 \sin^2x) \mathrm dx$ converge or diverge? Perhaps this is a better presentation of the proof's logic Nov 6 suggested approved edit on does $\int_0^\infty x/(1+x^2 \sin^2x) \mathrm dx$ converge or diverge? Nov 4 comment “Negative” versus “Minus” Why is this question protected and not closed as off-topic? It could well fit to Mathematics Education site, but not here in my opinion. Nov 4 comment Why is $Z_2 \times Z_3 \times Z_4$ not isomorphic to $Z_{24}$? Do 2 and 4 share no common factor?