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 A330219 #17 May 17 2021 08:50:31 %S A330219 39,55,56,63,68,80,128,136,144,155,156,171,184,196,203,208,219,220, %T A330219 252,256,259,275,291,292,323,328,355,363,387,388,400,475,507,568,592, %U A330219 603,667,723,763,772,955,1003,1027,1227,1243,1387,1411,1467,1507,1555 %N A330219 Negative discriminants with form class group isomorphic to C_4 (negated). %C A330219 It seems that this is the full list. %C A330219 Equivalently, negative discriminants of orders whose class group is isomorphic to C_4 (negated). - _Jianing Song_, May 17 2021 %H A330219 Rick L. Shepherd, <a href="http://libres.uncg.edu/ir/uncg/f/Shepherd_uncg_0154M_11099.pdf">Binary quadratic forms and genus theory</a>, Master of Arts Thesis, University of North Carolina at Greensboro, 2013 %o A330219 (PARI) isA330219(d) = (d>0) && ((d%4==0)||(d%4==3)) && quadclassunit(-d)[2]==[4] \\ _Jianing Song_, May 17 2021 %Y A330219 Cf. A133675 (negative discriminants with form class group isomorphic to the trivial group), A322710 (isomorphic to C_2), A328825 (isomorphic to C_3), A329182 (isomorphic to C_2 X C_2), this sequence (isomorphic to C_4). %Y A330219 Subsequence of A133676 and A317987. Cf. also A013658. %K A330219 nonn,fini %O A330219 1,1 %A A330219 _Jianing Song_, Dec 05 2019