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 A030254 #12 Feb 02 2023 15:07:31 %S A030254 0,0,54,12664 %N A030254 Number of nonisomorphic groupoids with 1 idempotent and a nontrivial symmetry. %H A030254 <a href="/index/Gre#groupoids">Index entries for sequences related to groupoids</a> %F A030254 a(n) = A030253(n) - A030271(n). %Y A030254 Column k=1 of A038020. %Y A030254 Cf. A030253, A030271. %K A030254 nonn,more %O A030254 1,3 %A A030254 _Christian G. Bower_ %E A030254 a(3) corrected by _Andrew Howroyd_, Feb 02 2023