A274553 Numbers k such that sigma(k) == 0 (mod k+4).

9, 56, 368, 780, 836, 2352, 11096, 17816, 45356, 77744, 91388, 128768, 254012, 388076, 430272, 2087936, 2291936, 13174976, 29465852, 35021696, 45335936, 120888092, 184773312, 260378492, 381236216, 775397948, 3381872252, 4856970752, 6800228816, 8589344768, 44257207676, 114141404156, 1461083549696, 1471763808896, 2199013818368

Offset: 1

Author

Paolo P. Lava, Jun 28 2016

Keywords

• nonn

Examples

			sigma(9) mod 9+4 = 13 mod 13 = 0.
		

Crossrefs

Cf. A045770, A067702, A088833, A181598, A274551, A274552, A274554-A274566.

Programs

Magma

[n: n in [1..2*10^6] | SumOfDivisors(n) mod (n+4) eq 0 ]; // Vincenzo Librandi, Jul 02 2016

Mathematica

k = 4; Select[Range[Abs@ k + 1, 10^6], Mod[DivisorSigma[1, #], # + k] == 0 &] (* Michael De Vlieger, Jul 01 2016 *)

Extensions

a(18)-a(35) from Giovanni Resta