A064145 a(n) = tau(n!-1) or number of divisors of n!-1.

1, 2, 2, 4, 2, 2, 4, 6, 4, 16, 2, 4, 2, 24, 4, 8, 8, 8, 4, 16, 8, 4, 4, 8, 4, 4, 16, 32, 2, 8, 2, 2, 4, 8, 4, 32, 2, 16, 4, 16, 16, 128, 16, 32, 32, 4, 16, 8, 4, 32, 32, 16, 64, 64, 32, 64, 32, 4, 8, 16, 16, 32, 16, 64, 16, 128, 4, 64, 32, 32, 8, 16, 32, 128, 8

Offset: 2

Author

Vladeta Jovovic, Sep 11 2001

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 2..135
• Hisanori Mishima, Factorizations of many number sequences

Crossrefs

Cf. A000005, A002582, A027423, A002981, A002982, A064144.

Programs

Mathematica

Do[ Print[ DivisorSigma[0, n! - 1]], {n, 2, 40} ]
DivisorSigma[0,Range[2,80]!-1] (* Harvey P. Dale, Aug 17 2024 *)

PARI

{ f=1; for (n=2, 100, f*=n; if (n>1, a=numdiv(f - 1), a=0); write("b064145.txt", n, " ", a) ) } \\ Harry J. Smith, Sep 09 2009

Extensions

More terms from Robert G. Wilson v, Oct 04 2001

a(51)-a(76) from Harry J. Smith, Sep 09 2009

Ambiguous term a(1) removed by Max Alekseyev, May 06 2022