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

4, 8925, 32445, 442365

Offset

1,1

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

Links

Table of n, a(n) for n=1..4.

Example

sigma(4) mod (4+3) = 7 mod 7 = 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, 3);

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

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

Sequence in context: A115050 A072724 A116271 * A257281 A201392 A058417

Adjacent sequences: A274548 A274549 A274550 * A274552 A274553 A274554

Keyword

nonn,more

Author

Paolo P. Lava, Jun 28 2016

Status

approved