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 A051996 #13 Sep 21 2021 14:44:56 %S A051996 1,-1,1,5,-1,3,-7,1,-3,-5,5,-11,1,-1,1,13,-1,7,-15,-3,5,-1,1,3,1,-5, %T A051996 21,-1,1,1,-13,-15,3,15,-31,1,-1,1,17,-35,-7,5,-1,1,19,-39,-3,-5,5,41, %U A051996 3,5,-23,1,1,-3,17,13,-1,-19,-29,1,-3,5,-31,21,33,-3,-7,35,3,1,-15,-19,-39,5,41,-21,-11,11,5,1,5,-55,55,29,5,-11,1,-35,35,1,-7,-3,1,1,-15,21 %N A051996 Consider real quadratic fields of ERD-type with class groups of exponent 2 and discriminants of the form D = r^2*k^2+k, k odd; sequence gives values of k. %D A051996 R. A. Mollin, Quadratics, CRC Press, 1996, Appendix A, Table A4(1), column k. %Y A051996 Cf. A051990, A051991, A051992, A051993, A051994, A051995, A051997, A051998. %K A051996 sign,fini,full %O A051996 1,4 %A A051996 _N. J. A. Sloane_, Jan 04 2000 %E A051996 a(73) and following from _Georg Fischer_, Sep 21 2021