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 A051986 #7 Sep 21 2021 07:09:20 %S A051986 394,865,1769,1985,2561,2762,3098,4385,5465,5485,5965,6122,7141,7265, %T A051986 10565,11101,11485,11581,13285,13466,14381,14765,16442,21365,22565, %U A051986 28373,34493,35197,36221,44861,47477,48485,48941,51365,54317 %N A051986 Discriminants of real quadratic fields with class number 2 and related continued fraction period length of 21. %D A051986 R. A. Mollin, Quadratics, CRC Press, 1996, Appendix A, Table A3. %H A051986 Georg Fischer, <a href="/A051986/b051986.txt">Table of n, a(n) for n = 1..59</a> %Y A051986 Cf. A051966-A051989. %K A051986 nonn,fini,full %O A051986 1,1 %A A051986 _N. J. A. Sloane_, Jan 04 2000