A364820 a(n) is the smallest prime factor of the n-th Pell number A000129(n).

2, 5, 2, 29, 2, 13, 2, 5, 2, 5741, 2, 33461, 2, 5, 2, 137, 2, 37, 2, 5, 2, 229, 2, 29, 2, 5, 2, 44560482149, 2, 61, 2, 5, 2, 13, 2, 593, 2, 5, 2, 1746860020068409, 2, 11437, 2, 5, 2, 3761, 2, 13, 2, 5, 2, 68480406462161287469, 2, 29, 2, 5, 2

Offset

2,1

Links

Amiram Eldar, Table of n, a(n) for n = 2..630

Formula

a(n) = A020639(A000129(n)).

Mathematica

FactorInteger[#][[1, 1]] & /@ LinearRecurrence[{2, 1}, {2, 5}, 57] (* Amiram Eldar, Oct 21 2023 *)

Crossrefs

Cf. A246556 (smallest primitive factor), A264137, A280104, A060383, A020639.

Sequence in context: A298664 A319201 A019295 * A373146 A328264 A170908

Adjacent sequences: A364817 A364818 A364819 * A364821 A364822 A364823

Keyword

nonn

Author

Sean A. Irvine, Oct 21 2023

Status

approved