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 A033267 #11 Jun 10 2018 02:37:23
%S A033267 21,24,30,33,40,42,45,48,57,60,70,72,78,85,88,93,102,112,130,133,177,
%T A033267 190,232,253
%N A033267 Numbers n such that every genus of binary quadratic forms of discriminant -4n consists of a single class and the class number h(-4n) = 4.
%D A033267 David A. Cox, "Primes of the Form x^2 + n y^2", Wiley, 1989, p. 60.
%D A033267 G. B. Mathews, Theory of Numbers, Chelsea, no date, p. 263.
%o A033267 (PARI) ok(n)={my(u=quadclassunit(-4*n).cyc); #u==2 && !select(t->t<>2, u)} \\ _Andrew Howroyd_, Jun 09 2018
%Y A033267 A subsequence of A000926.
%Y A033267 Cf. A033266, A033268, A033269.
%K A033267 nonn,fini,full
%O A033267 1,1
%A A033267 _N. J. A. Sloane_