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A057958 Number of prime factors of 3^n - 1 (counted with multiplicity). 18
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..660

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

FORMULA

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

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

PROG

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

CROSSREFS

Cf. A001222, A024023, A057951-A057958, A046051, A085028.

Sequence in context: A143309 A206562 A155981 * A225411 A247815 A057953

Adjacent sequences:  A057955 A057956 A057957 * A057959 A057960 A057961

KEYWORD

nonn

AUTHOR

Patrick De Geest, Nov 15 2000

EXTENSIONS

Offset corrected by Amiram Eldar, Feb 01 2020

STATUS

approved

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Last modified March 4 14:44 EST 2021. Contains 341796 sequences. (Running on oeis4.)