A363831 Number of divisors of A000129(n) (Pell numbers).

1, 2, 2, 6, 2, 8, 3, 16, 4, 8, 2, 72, 2, 12, 12, 40, 4, 32, 4, 96, 12, 16, 4, 384, 8, 16, 16, 144, 2, 288, 8, 96, 8, 32, 12, 1536, 8, 16, 16, 1024, 2, 288, 4, 384, 96, 32, 4, 3840, 12, 64, 32, 192, 2, 256, 32, 768, 32, 8, 2, 41472, 8, 64, 96, 896, 64, 256, 4

Offset: 1

Author

Tyler Busby, Oct 19 2023

Keywords

• nonn

Examples

			a(9)=4 because Pell(9)=985 has divisors {1, 5, 197, 985}.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..630 (calculated using Jon E. Schoenfield's a-file at A000129)

Crossrefs

Cf. A000005, A000129, A272040, A363829.

Programs

Mathematica

DivisorSigma[0,LinearRecurrence[{2,1},{1,2},67]] (* Stefano Spezia, Oct 19 2023 *)

Formula

a(n) = sigma0(Pell(n)) = A000005(A000129(n)).