A057958 Number of prime factors of 3^n - 1 (counted with multiplicity).

1, 3, 2, 5, 3, 5, 2, 7, 3, 6, 3, 8, 2, 5, 5, 10, 3, 8, 3, 10, 4, 7, 3, 11, 5, 5, 6, 9, 4, 11, 4, 12, 5, 8, 6, 12, 3, 7, 7, 13, 4, 11, 3, 11, 9, 6, 5, 17, 7, 10, 6, 9, 4, 13, 8, 13, 7, 9, 3, 17, 3, 8, 6, 14, 7, 12, 4, 12, 6, 11, 2, 16, 5, 8, 10, 11, 7, 15, 4, 18, 9, 8, 5, 18, 7, 6, 8, 16, 4, 19, 5

Offset: 1

Author

Patrick De Geest, Nov 15 2000

Keywords

• nonn

Links

• Max Alekseyev, Table of n, a(n) for n = 1..690 (first 660 terms from Amiram Eldar)
• S. S. Wagstaff, Jr., The Cunningham Project

Crossrefs

bigomega(b^n-1): A057951 (b=10), A057952 (b=9), A057953 (b=8), A057954 (b=7), A057955 (b=6), A057956 (b=5), A057957 (b=4), this sequence (b=3), A046051 (b=2).

Cf. A001222, A024023, A085028, A002591 A074477, A057952, A133801, A274909.

Programs

PARI

a(n)=bigomega(3^n-1) \\ Charles R Greathouse IV, Sep 14 2015

Formula

Mobius transform of A085028. - T. D. Noe, Jun 19 2003

a(n) = A001222(A024023(n)). - Amiram Eldar, Feb 01 2020

Extensions

Offset corrected by Amiram Eldar, Feb 01 2020