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 A051980 #7 Sep 21 2021 06:33:47 %S A051980 481,1417,1466,2858,3065,3589,3785,3977,4538,5317,5941,6641,6749,7082, %T A051980 11861,12701,12833,13793,14909,16589,17153,18185,18365,18581,20885, %U A051980 24221,27989,29069,32885,33365,44813,47165,51173,66197,67973,70493,78917 %N A051980 Discriminants of real quadratic fields with class number 2 and related continued fraction period length of 15. %D A051980 R. A. Mollin, Quadratics, CRC Press, 1996, Appendix A, Table A3. %Y A051980 Cf. A051966-A051989. %K A051980 nonn,fini,full %O A051980 1,1 %A A051980 _N. J. A. Sloane_, Jan 04 2000 %E A051980 a(16)=24221 and a(37) inserted by _Georg Fischer_, Sep 21 2021