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 A274556 #33 Jun 13 2025 08:21:25 %S A274556 2,3,4,6,7,8,11,12,18,21,26,68,656,2336,8768,133376,528896, %T A274556 34360918016,35184409837568,576460757135261696 %N A274556 Numbers k such that sigma(k) == 0 (mod k-5). %e A274556 sigma(6) (mod 6-5) = 12 mod 1 = 0. %t A274556 n = -5; Select[Range[1, 10^6], # + n != 0 && Mod[DivisorSigma[1, #], # + n] == 0 &] (* _Michael De Vlieger_, Jul 01 2016 *) %o A274556 (Magma) [n: n in [1..2*10^6] | n ne 5 and SumOfDivisors(n) mod (n-5) eq 0]; // _Vincenzo Librandi_, Jul 02 2016 %Y A274556 Contains subsequence A101223. %Y A274556 Cf. A067702, A223609, A274551, A274552, A274553, A274554, A274557, A274558, A274559, A274560, A274561, A274562, A274563, A274564, A274565, A274566. %K A274556 nonn,more %O A274556 1,1 %A A274556 _Paolo P. Lava_, Jun 30 2016 %E A274556 a(18) from _Giovanni Resta_, Jul 01 2016 %E A274556 Terms 2,3,4 inserted, a(19)-a(20) added by _Max Alekseyev_, May 25 2025