A366780 Number of distinct prime divisors of A000073(n) (tribonacci numbers).

0, 0, 1, 1, 1, 1, 2, 2, 1, 1, 2, 3, 2, 3, 2, 3, 1, 3, 4, 3, 3, 2, 2, 2, 3, 3, 3, 5, 3, 4, 5, 3, 4, 3, 5, 4, 5, 3, 5, 3, 2, 4, 2, 4, 5, 4, 4, 6, 2, 5, 5, 6, 3, 5, 7, 5, 2, 3, 5, 4, 6, 5, 4, 7, 3, 2, 4, 4, 3, 3, 4, 5, 2, 6, 6, 6, 5, 3, 6, 5, 4, 2, 6, 3, 6, 1, 7

Offset: 2

Author

Sean A. Irvine, Oct 22 2023

Keywords

• nonn

Examples

			a(8)=2 because the 8th tribonacci number 24 = 2^3*3 has 2 distinct prime factors.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 2..365

Crossrefs

Cf. A000073, A001221, A022307, A366781, A366782.

Programs

Mathematica

PrimeNu[LinearRecurrence[{1, 1, 1}, {1, 1, 2}, 87]] (* Amiram Eldar, Oct 23 2023 *)

Formula

a(n) = A001221(A000073(n)).