A274554 Numbers n such that sigma(n) == 0 (mod n-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

1,1

Comments

A125247 is a subset of this sequence.

Links

Table of n, a(n) for n=1..24.

Example

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

Maple

with(numtheory); P:=proc(q, h) local n;  for n from 1 to q do
if n+h>0 then if type(sigma(n)/(n+h), integer) then print(n); fi; fi; od; end: P(10^9, -4);

Mathematica

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

Prog

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

Crossrefs

Cf. A067702, A274551-A274553, A223609, A274566.

Sequence in context: A254227 A326806 A056050 * A035111 A035282 A075156

Adjacent sequences: A274551 A274552 A274553 * A274555 A274556 A274557

Keyword

nonn

Author

Paolo P. Lava, Jun 28 2016

Extensions

a(19)-a(24) from Giovanni Resta

Status

approved