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 A031606 #15 Aug 18 2021 00:10:32
%S A031606 82,2141,4274,6970,7306,10525,10937,14569,15053,18994,20389,24314,
%T A031606 25253,25889,30637,31337,36541,43793,47618,51701,52154,52609,53066,
%U A031606 54449,55381,62233,70537,71597,72665,80485,81050,82757,83905,85061,85642,86225,86810
%N A031606 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 18.
%t A031606 opct18Q[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]] == 18]; Select[Range[90000],opct18Q] (* _Harvey P. Dale_, Nov 12 2013 *)
%Y A031606 Subsequence of A003814.
%K A031606 nonn
%O A031606 1,1
%A A031606 _David W. Wilson_
%E A031606 Corrected by _Harvey P. Dale_, Nov 12 2013