A057941 Number of prime factors of 3^n + 1 (counted with multiplicity).

2, 2, 3, 2, 3, 3, 3, 3, 5, 4, 4, 3, 3, 4, 6, 2, 5, 4, 4, 3, 7, 4, 3, 6, 5, 4, 7, 4, 5, 6, 4, 2, 7, 4, 5, 4, 5, 4, 8, 5, 4, 7, 3, 5, 10, 4, 5, 4, 5, 8, 9, 4, 4, 5, 7, 6, 8, 4, 4, 7, 4, 5, 13, 2, 5, 6, 4, 5, 9, 9, 7, 8, 4, 5, 12, 6, 6, 7, 5, 5, 12, 5, 6, 10, 9, 7, 11, 6, 5, 9, 8, 4, 9, 4, 8, 6, 5, 9, 14, 6, 4

Offset

1,1

Links

Max Alekseyev, Table of n, a(n) for n = 1..691 (first 658 terms from Amiram Eldar)

S. S. Wagstaff, Jr., The Cunningham Project

Formula

a(n) = A057958(2n) - A057958(n) - T. D. Noe, Jun 19 2003

a(n) = A001222(A034472(n)). - Amiram Eldar, Feb 01 2020

Mathematica

PrimeOmega[3^Range[110]+1] (* Harvey P. Dale, Jun 20 2015 *)

Prog

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

Crossrefs

bigomega(b^n+1): A057934 (b=10), A057935 (b=9), A057936 (b=8), A057937 (b=7), A057938 (b=6), A057939 (b=5), A057940 (b=4), this sequence (b=3), A054992 (b=2).

Cf. A001222, A007658, A034472, A057958, A074476.

Sequence in context: A076235 A268058 A334686 * A358550 A126071 A338292

Adjacent sequences: A057938 A057939 A057940 * A057942 A057943 A057944

Keyword

nonn

Author

Patrick De Geest, Oct 15 2000

Status

approved