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A135621
Number of prime factors of 11^n + 2 (counted with multiplicity).
0
1, 1, 2, 2, 3, 1, 3, 3, 3, 1, 7, 3, 4, 3, 3, 2, 5, 2, 2, 3, 4, 3, 5, 3, 3, 3, 7, 3, 5, 6, 3, 2, 4, 3, 7, 5, 7, 3, 6, 3, 4, 4, 7, 4, 6, 7, 4, 2, 5, 3, 7, 5, 8, 4, 3, 4, 3, 5, 7, 6, 2, 5, 2, 5, 5, 4, 7, 7
OFFSET
0,3
COMMENTS
a(n)=1 for n=0,1,5,9,287,8273, see A109076.
EXAMPLE
a(0)=1 because 11^0+2=3(prime),
a(1)=1 because 11^1+2=13(prime),
a(2)=2 because 11^2+2=123=3*41(semiprime),
a(3)=2 because 11^3+2=123=31*43(semiprime),
a(4)=3 because 11^4+2=14643=3^2*1627(3 prime factors).
MATHEMATICA
Table[ PrimeOmega[11^n + 2] , {n, 0, 25}] (* G. C. Greubel, Oct 23 2016 *)
PROG
(PARI) a(n) = bigomega(11^n+2); \\ Michel Marcus, Oct 13 2013
CROSSREFS
Cf. A109076.
Sequence in context: A386730 A004595 A071681 * A369366 A224764 A077268
KEYWORD
nonn
AUTHOR
Zak Seidov, Mar 03 2008
STATUS
approved