Wok
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 Mar 18 comment Point closest to a set four of lines in 3D Ah, you are right. Mar 13 comment Point closest to a set four of lines in 3D Shouldn't it be $Ax=2b$ ? Nov 5 comment Distributions of point charges Thanks. I updated the link. Great webpage! Nov 5 revised Distributions of point charges URL change Aug 19 awarded Popular Question Aug 4 awarded Yearling Jul 30 comment What is the name of this shape? (spacetime) Missing image of the shape. Not easy to answer then. Jul 3 asked Find the Lipschitz constant of a multi-variate Gaussian density function Apr 22 awarded Good Answer Apr 4 awarded Curious Sep 30 awarded Explainer Sep 24 awarded Autobiographer Sep 4 comment Closed form for the sequence defined by $a_0=1$ and $a_{n+1} = a_n + a_n^{-1}$ I guess positivity of $\varphi$ is one sufficient condition to get the correct behavior. Only a guess though. Aug 4 awarded Yearling Mar 12 comment Is $0$ a natural number? This question is not related to math, it is the consequence of an ambiguous notation which was used by Dedekind in 1888. To avoid ambiguity, ℕ* is used to exclude 0. I cannot manage to understand how this question is still not closed. Mar 12 comment Simple combinatorics question - caught off guard! I see your point, yet I believe it is a shame to have ambiguous statements in math. Mar 12 comment Simple combinatorics question - caught off guard! With Wiki, "there is no universal agreement about whether to include zero in the set of natural numbers: some define the natural numbers to be the positive integers {1, 2, 3, ...}, while for others the term designates the non-negative integers {0, 1, 2, 3, ...}. The former definition is the traditional one, with the latter definition having first appeared in the 19th century." In the context, this is ambiguous since "For natural numbers (taken to include 0) n and k", the binomial coef is defined Mar 12 comment Simple combinatorics question - caught off guard! Not in my country. In France, we call ℕ* the set excluding 0. Mar 12 comment Simple combinatorics question - caught off guard! This is wrong for n=0. Mar 12 comment Simple combinatorics question - caught off guard! This is clear and intuitive. However, one would have to take care of the case for which a pair contains twice the same "menu" (n=0), and for which the statement is wrong.