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 A031628 #14 Aug 18 2021 00:10:32
%S A031628 401,10429,20498,32842,33937,68813,90826,92641,94474,178525,180217,
%T A031628 213973,214898,216754,251626,252629,253634,254641,256661,257674,
%U A031628 259706,262769,344237,346585,348941,353677,386602,392837,396602,400385,439333,443314,449989
%N A031628 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 40.
%t A031628 op40Q[n_]:=Module[{s=Sqrt[n],cf,len},cf=If[IntegerQ[s],{0,0}, ContinuedFraction[ s][[2]]];len=Length[cf];OddQ[len]&&cf[[(len+1)/2]] ==40]; Select[Range[500000],op40Q] (* _Harvey P. Dale_, Dec 06 2015 *)
%Y A031628 Subsequence of A003814.
%K A031628 nonn
%O A031628 1,1
%A A031628 _David W. Wilson_
%E A031628 Corrected and extended by _Harvey P. Dale_, Dec 06 2015