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 A031621 #14 Aug 18 2021 00:10:32 %S A031621 2509,13738,23185,61729,64234,79813,80378,81514,83233,98957,101485, %T A031621 102761,147218,150298,151073,152629,171194,172021,175349,176186, %U A031621 177866,178709,180401,205033,231241,233165,235097,238985,263105,265157,267217 %N A031621 Numbers k such that the continued fraction for sqrt(k) has odd period and if the last term of the periodic part is deleted the two central terms are both 33. %Y A031621 Subsequence of A003814. %K A031621 nonn %O A031621 1,1 %A A031621 _David W. Wilson_ %E A031621 First term 1090 removed by _Georg Fischer_, Jun 16 2019