A135621 Number of prime factors of 11^n + 2 (counted with multiplicity).

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

Author

Zak Seidov, Mar 03 2008

Keywords

• nonn

Comments

a(n)=1 for n=0,1,5,9,287,8273, see A109076.

Examples

			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).
		

Crossrefs

Cf. A109076.

Programs

Mathematica

Table[ PrimeOmega[11^n + 2] , {n,0,25}] (* G. C. Greubel, Oct 23 2016 *)

PARI

a(n) = bigomega(11^n+2); \\ Michel Marcus, Oct 13 2013