This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A364820 #15 Oct 21 2023 17:11:55
%S A364820 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,
%T A364820 44560482149,2,61,2,5,2,13,2,593,2,5,2,1746860020068409,2,11437,2,5,2,
%U A364820 3761,2,13,2,5,2,68480406462161287469,2,29,2,5,2
%N A364820 a(n) is the smallest prime factor of the n-th Pell number A000129(n).
%H A364820 Amiram Eldar, <a href="/A364820/b364820.txt">Table of n, a(n) for n = 2..630</a>
%F A364820 a(n) = A020639(A000129(n)).
%t A364820 FactorInteger[#][[1, 1]] & /@ LinearRecurrence[{2, 1}, {2, 5}, 57] (* _Amiram Eldar_, Oct 21 2023 *)
%Y A364820 Cf. A246556 (smallest primitive factor), A264137, A280104, A060383, A020639.
%K A364820 nonn
%O A364820 2,1
%A A364820 _Sean A. Irvine_, Oct 21 2023