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 A274554 #26 Jun 14 2025 17:52:49 %S A274554 5,6,10,22,24,60,130,184,1012,2272,18904,33664,70564,85936,100804, %T A274554 391612,527872,1090912,17619844,2147713024,6800695312,34360655872, %U A274554 549759483904,1661355408388 %N A274554 Numbers k such that sigma(k) == 0 (mod k-4). %C A274554 A125247 is a subset of this sequence. %e A274554 sigma(5) (mod 5-4) = 6 (mod 1) = 0. %p A274554 q:= k-> is(irem(numtheory[sigma](k), k-4)=0): %p A274554 select(q, [$5..400000])[]; # _Alois P. Heinz_, Jun 14 2025 %t A274554 k = -4; Select[Range[Abs@ k + 1, 10^7], Mod[DivisorSigma[1, #], # + k] == 0 &] (* _Michael De Vlieger_, Jul 01 2016 *) %o A274554 (Magma) [n: n in [5..2*10^6] | SumOfDivisors(n) mod (n-4) eq 0 ]; // _Vincenzo Librandi_, Jul 02 2016 %Y A274554 Cf. A067702, A125247, A223609, A274551, A274552, A274553, A274566. %K A274554 nonn,more %O A274554 1,1 %A A274554 _Paolo P. Lava_, Jun 28 2016 %E A274554 a(19)-a(24) from _Giovanni Resta_, Jul 01 2016