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 A325654 #26 Jul 25 2025 19:25:31 %S A325654 6,28,496,8128,60480,65520,4357080,33550336,47139840,91065600, %T A325654 285981696,2758909440,8589869056,87722956800,132867440640, %U A325654 137438691328,306007080960,806062473216,1409150457792,363485766938112,12177456042320640,29884246553283840 %N A325654 Numbers m with a divisor d satisfying sigma(d) = 2*m. %C A325654 Even perfect numbers from A000396 are terms. %C A325654 Numbers of the form A007691(k)*A054030(k)/2 when A054030(k) is even. %C A325654 Subsequence of A323652. %C A325654 Numbers of the form sigma(A325637(k))/2. - _Jinyuan Wang_, Jun 09 2019 %H A325654 Vaclav Kotesovec, <a href="/A325654/b325654.txt">Table of n, a(n) for n = 1..1000</a> %e A325654 60480 is a term because 30240 divides 60480 and sigma(30240) = 120960 = 2*60480. %o A325654 (Magma) [n: n in [1..100000] | #[d: d in Divisors(n) | SumOfDivisors(d) eq 2*n] gt 0]; %o A325654 (PARI) isok(n) = fordiv(n, d, if (sigma(d) == 2*n, return(1))); 0; \\ _Michel Marcus_, May 12 2019 %Y A325654 Cf. A000203, A000396, A007691, A054030, A323652, A325637. %K A325654 nonn %O A325654 1,1 %A A325654 _Jaroslav Krizek_, May 12 2019 %E A325654 More terms from _Jinyuan Wang_, Jun 09 2019