A015995 a(n) = (tau(n^3)+2)/3.

1, 2, 2, 3, 2, 6, 2, 4, 3, 6, 2, 10, 2, 6, 6, 5, 2, 10, 2, 10, 6, 6, 2, 14, 3, 6, 4, 10, 2, 22, 2, 6, 6, 6, 6, 17, 2, 6, 6, 14, 2, 22, 2, 10, 10, 6, 2, 18, 3, 10, 6, 10, 2, 14, 6, 14, 6, 6, 2, 38, 2, 6, 10, 7, 6, 22, 2, 10, 6, 22, 2, 24, 2, 6, 10, 10, 6, 22, 2, 18, 5, 6, 2, 38, 6, 6

Offset: 1

Author

Robert G. Wilson v

Keywords

• nonn

Links

• Antti Karttunen, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A004194, A018892, A015996, A015999, A016001, A016002, A016003, A016005-A016009, A016012, A016017, A016018, A016020, A016025, A048785.

Programs

Mathematica

Table[(DivisorSigma[0,n^3]+2)/3,{n,90}] (* Harvey P. Dale, Apr 30 2018 *)

PARI

a(n)=(numdiv(n^3)+2)/3 \\ Charles R Greathouse IV, May 01 2013

PARI

a(n)=my(f=factor(n)[,2]);prod(i=1,#f,3*f[i]+1)\3+1 \\ Charles R Greathouse IV, May 01 2013

Formula

a(n) = (2+A048785(n))/3. - R. J. Mathar, May 07 2021

Extensions

Definition corrected by Vladeta Jovovic, Sep 03 2005