A166281 Number of ordered factorizations of the nonprimes (A018252).

1, 2, 3, 4, 2, 3, 8, 3, 3, 8, 8, 8, 3, 3, 20, 2, 3, 4, 8, 13, 16, 3, 3, 3, 26, 3, 3, 20, 13, 8, 8, 3, 48, 2, 8, 3, 8, 20, 3, 20, 3, 3, 44, 3, 8, 32, 3, 13, 8, 3, 13, 76, 3, 8, 8, 3, 13, 48, 8, 3, 44, 3, 3, 3, 20, 44, 3, 8, 3, 3, 3, 112, 8, 8, 26, 13, 20, 13, 3

Offset: 1

Author

Juri-Stepan Gerasimov, Oct 10 2009

Keywords

• nonn
• easy

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A002033, A018252, A035004, A074206.

Programs

Mathematica

f[1] = 1; f[n_] := f[n] = DivisorSum[n, f[#] &, # < n &]; f /@ Select[Range[100], ! PrimeQ[#] &] (* Amiram Eldar, May 01 2025 *)

Formula

a(n) = A002033(A018252(n)-1). - R. J. Mathar, Oct 14 2009

a(n) = A074206(A018252(n)). - Amiram Eldar, May 01 2025

Extensions

Entries checked by R. J. Mathar, Oct 14 2009

Name corrected by Amiram Eldar, May 01 2025