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 A188937 #7 Oct 12 2017 10:05:24 %S A188937 2,3,3,4,5,6,8,9,6,10,7,6,9,8,10 %N A188937 Let G be the class group of the imaginary quadratic field Q(sqrt(-A188661(n))); the 2-Sylow subgroup of G is cyclic of order 2^a(n). %H A188937 Daniel Shanks, <a href="https://doi.org/10.1090/S0025-5718-1971-0297737-4">Gauss's ternary form reduction and the 2-Sylow subgroup</a>, Math. Comp. 25 (1971), 837-853. %K A188937 nonn,more %O A188937 1,1 %A A188937 _N. J. A. Sloane_, Apr 14 2011