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 A003171 M2331 N0922 #35 Dec 03 2019 03:22:03
%S A003171 3,4,7,8,11,12,15,16,19,20,24,27,28,32,35,36,40,43,48,51,52,60,64,67,
%T A003171 72,75,84,88,91,96,99,100,112,115,120,123,132,147,148,160,163,168,180,
%U A003171 187,192,195,228,232,235,240,267,280,288,312,315,340,352,372,403
%N A003171 Negated discriminants of orders of imaginary quadratic fields with 1 class per genus (a finite sequence).
%C A003171 It is conjectured that a(101) = 7392 is the last term. If it would exist, a(102) > 10^6. - _Hugo Pfoertner_, Dec 01 2019
%D A003171 Z. I. Borevich and I. R. Shafarevich, Number Theory. Academic Press, NY, 1966, pp. 425-430.
%D A003171 L. E. Dickson, Introduction to the Theory of Numbers. Dover, NY, 1957, p. 85.
%D A003171 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
%D A003171 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H A003171 Andrew Howroyd, <a href="/A003171/b003171.txt">Table of n, a(n) for n = 1..101</a>
%H A003171 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.
%H A003171 Jianing Song, <a href="/A003171/a003171.txt">List of the corresponding class groups</a>
%o A003171 (PARI) ok(n)={(-n)%4<2 && !#select(k->k<>2, quadclassunit(-n).cyc)} \\ _Andrew Howroyd_, Jul 20 2018
%Y A003171 Cf. A000926, A133288.
%Y A003171 The fundamental terms are given in A003644.
%K A003171 nonn,fini
%O A003171 1,1
%A A003171 _N. J. A. Sloane_, _Mira Bernstein_
%E A003171 Terms a(44) and beyond from _Andrew Howroyd_, Jul 20 2018