This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A325637 #25 Jun 27 2024 01:43:22 %S A325637 6,28,496,8128,30240,32760,2178540,23569920,33550336,45532800, %T A325637 142990848,1379454720,8589869056,43861478400,66433720320,137438691328, %U A325637 153003540480,403031236608,704575228896,181742883469056,6088728021160320,14942123276641920,20158185857531904,275502900594021408,622286506811515392,2305843008139952128 %N A325637 Numbers k for which gcd(2k, sigma(k)) = 2k. %C A325637 Multiply-perfect numbers (A007691) k with an even abundancy index sigma(k)/k. - _Amiram Eldar_, Jun 26 2024 %H A325637 Antti Karttunen, <a href="/A325637/b325637.txt">Table of n, a(n) for n = 1..1013</a> (computed from the b-file of A007691 prepared by T. D. Noe, using Flammenkamp's data) %H A325637 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>. %H A325637 <a href="/index/O#opnseqs">Index entries for sequences where any odd perfect numbers must occur</a>. %F A325637 a(n) = A224832(n)/2. - _Amiram Eldar_, Jun 26 2024 %o A325637 (PARI) isA325637(n) = ((n+n)==gcd(n+n,sigma(n))); %Y A325637 Cf. A000203, A033879, A224832, A325636, A325638, A325654. %Y A325637 Subsequences: A000396, A336702 (after its initial 1). %Y A325637 Subsequence of A007691. %K A325637 nonn %O A325637 1,1 %A A325637 _Antti Karttunen_, May 21 2019