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 A051991 #9 Sep 21 2021 15:46:08 %S A051991 34,51,66,87,102,119,123,138,146,194,215,231,258,287,318,330,390,402, %T A051991 410,435,447,455,482,527,570,615,623,627,635,678,770,782,798,843,890, %U A051991 902,1022,1095,1235,1298,1302,1515,1547,1610,1770,1938,1995 %N A051991 Discriminants of real quadratic fields of ERD-type with class groups of exponent 2 and discriminants of the form D = r^2*k^2+2k, k odd. %C A051991 Excludes discriminants appearing in A051990. %D A051991 R. A. Mollin, Quadratics, CRC Press, 1996, Appendix A, Table A4(2), column D. %H A051991 Georg Fischer, <a href="/A051991/b051991.txt">Table of n, a(n) for n = 1..76</a> %Y A051991 Cf. A051990, A051992, A051993, A051994, A051995, A051996, A051997, A051998. %K A051991 nonn,fini,full %O A051991 1,1 %A A051991 _N. J. A. Sloane_, Jan 04 2000