A359455 Expansion of Sum_{k>0} x^k / (1 - x^(k^3)).

1, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 3, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 3, 3, 2, 2, 2, 2, 2, 2, 2, 3, 2, 3, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 3, 2, 3, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2

Offset: 1

Author

Seiichi Manyama, Jan 06 2023

Keywords

• nonn
• easy

Comments

Number of divisors d of n such that d^3 | (n - d).

Links

• Seiichi Manyama, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000005, A163671.

Programs

Mathematica

a[n_] := DivisorSum[n, 1 &, Divisible[n-#, #^3] &]; Array[a, 100] (* Amiram Eldar, Aug 14 2023 *)

PARI

a(n) = sumdiv(n, d, (n-d)%d^3==0);