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 A344408 #13 May 18 2021 04:07:41 %S A344408 40,60,65,85,96,104,105,120,136,140,156,160,165,168,185,192,200,204, %T A344408 205,220,221,224,232,240,252,260,264,265,273,280,285,288,296,300,305, %U A344408 312,320,325,336,340,345,348,352,357,360,364,365,377,380,384,385,408 %N A344408 Positive discriminants of orders with class number 2. %C A344408 Also positive discriminants of orders with class group isomorphic to C_2. %C A344408 The fundamental terms are listed in A094619. %H A344408 Jianing Song, <a href="/A344408/b344408.txt">Table of n, a(n) for n = 1..10001</a> %o A344408 (PARI) isA344408(d) = (d>0) && !issquare(d) && ((d%4==0)||(d%4==1)) && quadclassunit(d)[2]==[2] %Y A344408 Cf. A133315 (positive discriminants of orders with class number 1), this sequence (class number 2), A344409 (class number 3). %Y A344408 Cf. A322710 (the negative discriminant case), A094619. %K A344408 nonn %O A344408 1,1 %A A344408 _Jianing Song_, May 17 2021