A363027 Sum of divisors of 5*n-4 of form 5*k+2.

0, 2, 0, 2, 7, 2, 0, 14, 0, 2, 17, 9, 0, 24, 0, 2, 27, 2, 7, 46, 0, 2, 37, 2, 0, 51, 0, 19, 47, 2, 0, 66, 7, 2, 57, 24, 0, 64, 0, 9, 67, 2, 0, 113, 17, 2, 84, 2, 0, 84, 0, 34, 87, 9, 0, 106, 0, 24, 97, 39, 7, 121, 0, 2, 107, 2, 0, 175, 0, 2, 144, 2, 0, 124, 7, 49, 127, 2, 17, 168, 0, 9, 137, 86, 0, 144, 0, 2

Offset

1,2

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Formula

a(n) = A284280(5*n-4).

G.f.: Sum_{k>0} (5*k-3) * x^(3*k-1) / (1 - x^(5*k-3)).

Maple

f:= n ->
  convert(select(t -> t mod 5 = 2, numtheory:-divisors(5*n-4)), `+`):
map(f, [$1..100]); # Robert Israel, Jul 23 2023

Mathematica

a[n_] := DivisorSum[5*n - 4, # &, Mod[#, 5] == 2 &]; Array[a, 100] (* Amiram Eldar, Jul 06 2023 *)

Prog

(PARI) a(n) = sumdiv(5*n-4, d, (d%5==2)*d);

Crossrefs

Cf. A362952, A363025, A363026.

Cf. A284280, A359244, A363032.

Sequence in context: A185343 A161014 A344768 * A235712 A154852 A088996

Adjacent sequences: A363024 A363025 A363026 * A363028 A363029 A363030

Keyword

nonn,look

Author

Seiichi Manyama, Jul 06 2023

Status

approved