A274554 Numbers k such that sigma(k) == 0 (mod k-4).

5, 6, 10, 22, 24, 60, 130, 184, 1012, 2272, 18904, 33664, 70564, 85936, 100804, 391612, 527872, 1090912, 17619844, 2147713024, 6800695312, 34360655872, 549759483904, 1661355408388

Offset: 1

Author

Paolo P. Lava, Jun 28 2016

Keywords

• nonn
• more

Comments

A125247 is a subset of this sequence.

Examples

			sigma(5) (mod 5-4) = 6 (mod 1) = 0.
		

Crossrefs

Cf. A067702, A125247, A223609, A274551, A274552, A274553, A274566.

Programs

Magma

[n: n in [5..2*10^6] | SumOfDivisors(n) mod (n-4) eq 0 ]; // Vincenzo Librandi, Jul 02 2016

Maple

q:= k-> is(irem(numtheory[sigma](k), k-4)=0):
select(q, [$5..400000])[];  # Alois P. Heinz, Jun 14 2025

Mathematica

k = -4; Select[Range[Abs@ k + 1, 10^7], Mod[DivisorSigma[1, #], # + k] == 0 &] (* Michael De Vlieger, Jul 01 2016 *)

Extensions

a(19)-a(24) from Giovanni Resta, Jul 01 2016