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

1,4

Links

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

Formula

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

Example

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

Mathematica

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

Crossrefs

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

Sequence in context: A305611 A325765 A032741 * A353338 A319149 A344462

Adjacent sequences: A364815 A364816 A364817 * A364819 A364820 A364821

Keyword

nonn

Author

Tyler Busby, Oct 21 2023

Status

approved