1,3

Table of n, a(n) for n=1..99.

Eric Weisstein's World of Mathematics, Prime Factor.

a(n) = omega(3^n - 1) = A001221(3^n - 1)

a(4) = omega(3^4 - 1) = omega(80) = omega(2^4 * 5) = 2.

Table[PrimeNu[3^n - 1], {n, 1, 50}] (* G. C. Greubel, May 21 2017 *)

(PARI) for(n = 1, 100, print1(omega(3^n - 1), ", "))

Cf. A001221, A113913.

Sequence in context: A299230 A182576 A128330 * A181630 A112310 A137734

Adjacent sequences: A133798 A133799 A133800 * A133802 A133803 A133804

nonn

Ryan Propper, Jan 06 2008

approved