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

4, 8925, 32445, 442365, 151115727449904501489664

Offset

1,1

Comments

Contains 2^(m-1)*(2^m-7) for m in A059609. - Max Alekseyev, Oct 11 2025

Links

Table of n, a(n) for n=1..5.

Example

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

Mathematica

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

Prog

(PARI) is(n) = Mod(sigma(n), n+3)==0 \\ Felix Fröhlich, Jul 01 2016
(Magma) [n: n in [1..2*10^6] | SumOfDivisors(n) mod (n+3) eq 0 ]; // Vincenzo Librandi, Jul 02 2016

Crossrefs

Contains A087167 as a subsequence.

Cf. A000203, A059609, A067702, A088834, A274552, A274553, A274554, A274556.

Sequence in context: A115050 A072724 A116271 * A257281 A201392 A389560

Adjacent sequences: A274548 A274549 A274550 * A274552 A274553 A274554

Keyword

nonn,hard,more

Author

Paolo P. Lava, Jun 28 2016

Extensions

a(5) from Max Alekseyev, Oct 11 2025

Status

approved