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 A051997 #12 Sep 21 2021 15:47:19 %S A051997 -1,1,1,3,1,-1,1,-3,1,-1,-5,3,1,-1,-3,3,-5,1,5,-3,3,7,-1,-1,-3,-5,-1, %T A051997 1,5,1,-7,-1,7,1,-5,1,-1,3,5,1,3,-3,13,5,3,1,-15,-5,3,-7,7,-3,3,13,-3, %U A051997 -11,3,-15,1,-1,-21,-33,15,3,-3,-5,5,-17,7,3,5,1,-5,7,3,-13 %N A051997 Consider 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; sequence gives values of k. %C A051997 Excludes discriminants appearing in A051990. %D A051997 R. A. Mollin, Quadratics, CRC Press, 1996, Appendix A, Table A4(2), column k. %Y A051997 Cf. A051990, A051991, A051992, A051993, A051994, A051995, A051996, A051998. %K A051997 sign,fini,full %O A051997 1,4 %A A051997 _N. J. A. Sloane_, Jan 04 2000 %E A051997 Offset changed to 1 by _Georg Fischer_, Sep 21 2021