A274556 Numbers k such that sigma(k) == 0 (mod k-5).

2, 3, 4, 6, 7, 8, 11, 12, 18, 21, 26, 68, 656, 2336, 8768, 133376, 528896, 34360918016, 35184409837568, 576460757135261696

Offset: 1

Author

Paolo P. Lava, Jun 30 2016

Keywords

• nonn
• more

Examples

			sigma(6) (mod 6-5) = 12 mod 1 = 0.
		

Crossrefs

Contains subsequence A101223.

Cf. A067702, A223609, A274551, A274552, A274553, A274554, A274557, A274558, A274559, A274560, A274561, A274562, A274563, A274564, A274565, A274566.

Programs

Magma

[n: n in [1..2*10^6] | n ne 5 and SumOfDivisors(n) mod (n-5) eq 0]; // Vincenzo Librandi, Jul 02 2016

Mathematica

n = -5; Select[Range[1, 10^6], # + n != 0 && Mod[DivisorSigma[1, #], # + n] == 0 &] (* Michael De Vlieger, Jul 01 2016 *)

Extensions

a(18) from Giovanni Resta, Jul 01 2016

Terms 2,3,4 inserted, a(19)-a(20) added by Max Alekseyev, May 25 2025