A359943 a(n) = Sum_{d|n, d-1 is cube} d.

1, 3, 1, 3, 1, 3, 1, 3, 10, 3, 1, 3, 1, 3, 1, 3, 1, 12, 1, 3, 1, 3, 1, 3, 1, 3, 10, 31, 1, 3, 1, 3, 1, 3, 1, 12, 1, 3, 1, 3, 1, 3, 1, 3, 10, 3, 1, 3, 1, 3, 1, 3, 1, 12, 1, 31, 1, 3, 1, 3, 1, 3, 10, 3, 66, 3, 1, 3, 1, 3, 1, 12, 1, 3, 1, 3, 1, 3, 1, 3, 10, 3, 1, 31, 1, 3

Offset: 1

Author

Seiichi Manyama, Jan 19 2023

Keywords

• nonn

Crossrefs

Cf. A001093, A113061, A359937, A359942, A359944.

Programs

Mathematica

a[n_] := DivisorSum[n, # &, IntegerQ[Surd[#-1, 3]] &]; Array[a, 100] (* Amiram Eldar, Aug 09 2023 *)

PARI

a(n) = sumdiv(n, d, ispower(d-1, 3)*d);

Formula

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