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A057951
Number of prime factors of 10^n - 1 (counted with multiplicity).
26
2, 3, 4, 4, 4, 7, 4, 6, 6, 6, 4, 9, 5, 6, 8, 8, 4, 11, 3, 9, 9, 9, 3, 12, 7, 8, 9, 10, 7, 15, 5, 13, 8, 8, 9, 14, 5, 5, 8, 13, 6, 17, 6, 13, 12, 8, 4, 15, 6, 12, 10, 11, 6, 16, 10, 14, 8, 10, 4, 22, 9, 7, 16, 17, 9, 17, 5, 12, 8, 14, 4, 20, 5, 9, 14, 8, 10, 18
OFFSET
1,1
LINKS
Max Alekseyev, Table of n, a(n) for n = 1..352 (first 322 terms from Ray Chandler)
S. S. Wagstaff, Jr., Main Tables from the Cunningham Project.
S. S. Wagstaff, Jr., The Cunningham Project
FORMULA
Mobius transform of A085035 - T. D. Noe, Jun 19 2003
a(n) = Omega(10^n -1) = Omega(R_n) + 2 = A046053(n) + 2 {where Omega(n) = A001222(n) and R_n = (10^n - 1)/9 = A002275(n)}. - Lekraj Beedassy, Jun 09 2006
a(n) = A001222(A002283(n)). - Ray Chandler, Apr 22 2017
MATHEMATICA
PrimeOmega[10^Range[70]-1] (* Jayanta Basu, May 29 2013 *)
PROG
(PARI) a(n)=bigomega(10^n-1) \\ Charles R Greathouse IV, Sep 14 2015
CROSSREFS
bigomega(b^n-1): this sequence (b=10), A057952 (b=9), A057953 (b=8), A057954 (b=7), A057955 (b=6), A057956 (b=5), A057957 (b=4), A057958 (b=3), A046051 (b=2).
Sequence in context: A344351 A108355 A346049 * A076410 A361164 A309941
KEYWORD
nonn
AUTHOR
Patrick De Geest, Nov 15 2000
EXTENSIONS
Erroneous b-file replaced by Ray Chandler, Apr 26 2017
STATUS
approved