A364818 Number of distinct prime divisors of A000129(n) (Pell numbers).

0, 1, 1, 2, 1, 3, 1, 3, 2, 3, 1, 5, 1, 3, 3, 4, 2, 5, 2, 6, 3, 4, 2, 7, 3, 4, 4, 6, 1, 7, 3, 5, 3, 5, 3, 9, 3, 4, 4, 9, 1, 7, 2, 8, 6, 5, 2, 10, 3, 6, 5, 7, 1, 8, 5, 8, 5, 3, 1, 13, 3, 6, 6, 8, 6, 8, 2, 9, 4, 8, 3, 13, 2, 7, 8, 9, 5, 10, 4, 12, 7, 5, 2, 14, 7

Offset: 1

Author

Tyler Busby, Oct 21 2023

Keywords

• nonn

Examples

			a(8)=3 because Pell(8)=408 has prime factors {2, 2, 2, 3, 17}.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..630

Crossrefs

Cf. A000129, A001221, A272040, A363829, A363831, A363833.

Programs

Mathematica

PrimeNu[LinearRecurrence[{2, 1}, {1, 2}, 85]] (* Amiram Eldar, Oct 21 2023 *)

Formula

a(n) = omega(Pell(n)) = A001221(A000129(n)).