A274551 Numbers k such that sigma(k) == 0 (mod k+3).

4, 8925, 32445, 442365

Offset: 1

Author

Paolo P. Lava, Jun 28 2016

Keywords

• nonn
• more

Comments

a(5) > 10^8 if it exists. - Felix Fröhlich, Jul 01 2016

No more terms < 6.5*10^14. - Jud McCranie, Dec 02 2019

No more terms < 2.7*10^15. - Jud McCranie, Jul 27 2025

Examples

			sigma(4) mod (4+3) = 7 mod 7 = 0.
		

Crossrefs

Cf. A000203, A067702, A087167, A088834, A274552, A274553, A274554, A274556.

Programs

Magma

[n: n in [1..2*10^6] | SumOfDivisors(n) mod (n+3) eq 0 ]; // Vincenzo Librandi, Jul 02 2016

Mathematica

Select[Range[10^6], Mod[DivisorSigma[1, #], # + 3] == 0 &] (* Michael De Vlieger, Jul 01 2016 *)

PARI

is(n) = Mod(sigma(n), n+3)==0 \\ Felix Fröhlich, Jul 01 2016