Esteban Crespi
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 Feb 11 reviewed Approve There are two buckets A and B. Dec 9 reviewed Edit Finding a matrix knowing determinant Dec 9 revised Finding a matrix knowing determinant edited body Dec 7 reviewed Approve Joint Likelihood Nov 28 revised On a generalization for $\sum_{d|n}rad(d)\phi(\frac{n}{d})$ and related questions added 1275 characters in body Nov 27 answered On a generalization for $\sum_{d|n}rad(d)\phi(\frac{n}{d})$ and related questions Nov 27 reviewed Edit Solve the pde : $x^2(y-z)\,\partial_x(z)+y^2(z-x)\,\partial_y(z)=z^2(x-y)$ Nov 27 revised Solve the pde : $x^2(y-z)\,\partial_x(z)+y^2(z-x)\,\partial_y(z)=z^2(x-y)$ mathjax and typo Nov 27 reviewed Approve Finding mass of a sphere given density = $1-\rho^2$ and radius = 1 Nov 10 reviewed Reject Maximize sum of numbers subject to an upper bound of the sum of each of these numbers raised to an arbitrary power Nov 10 comment Numbers $n$ whose prime factors are $2$ and $5$ if and only if $\sum_{k=1}^{rad(n)}\mu(k)k=0$? For $n$ small n=10 is the only solution to $\sum_{k=1}^n \mu(k)k=0$. This means that $\sum_{k=1}^{\operatorname{rad}(n)} \mu(k)k=0$, for all the members of the sequence A033846 as they all have $\operatorname{rad}(n) = 10$. The term $\sum_{k=1}^{\operatorname{rad}(n)} k=0$ seems to be an error. Nov 8 awarded Yearling Nov 5 awarded Critic Nov 5 awarded Custodian Nov 5 reviewed Approve Complex integration upper semi-circle $\int f(z)dz$ when $r>1$ Oct 21 awarded number-theory Oct 14 answered Finding $\sum_{i = 1}^{n} \frac{n} { \gcd(i, n)}$ Oct 7 answered Is it possible to subtract a perfect square from another number to make it a perfect square? Oct 5 answered Sanity check: prime ideals in number fields Sep 24 revised Factorization in a Group Added a reference and modification of the answer.