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 A278582 #5 Nov 30 2016 05:10:40 %S A278582 20,21,24,32,48,64,72,96,100,144,147,199,288,576 %N A278582 Numbers n such that the Shimura subgroup Sigma(n) of the Jacobi variety J_0(n) has order 2. %D A278582 Ling, S., and J. Oesterlé. "The Shimura subgroup of J_0(N)." Astérisque, Vol. 196-197 (1991), 171-203. %Y A278582 Cf. A278581. %K A278582 nonn,fini,full %O A278582 1,1 %A A278582 _N. J. A. Sloane_, Nov 30 2016