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 A230109 #8 Oct 09 2013 11:28:16 %S A230109 3,7,12,13,19,21,27,28,31,39,43,48,52,57,61,63,67,73,75,76,84,91,93, %T A230109 97,103,108,109,111,112,117,124,127,129,133,139,147,151,156,157,163, %U A230109 171,172,175 %N A230109 Values of d such that the equation x^2 - d*y^2 = 3*d has integer solutions. %e A230109 43 appears in the sequence because the equation x^2 - 43*y^2 = 129 has integer solutions, such as (x,y) = (86,13). %Y A230109 Cf. A172000, A230108. %K A230109 nonn %O A230109 1,1 %A A230109 _Colin Barker_, Oct 09 2013