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 A051758 #7 Oct 05 2021 00:28:48 %S A051758 1,4,2,1,1,5,2,15 %N A051758 Consider problem of placing A051755(n) queens on an n X n board so that each queen attacks precisely 2 others. Sequence gives number of solutions up to square symmetry. %Y A051758 Cf. A051754-A051759, A051567-A051571, A019654. %K A051758 nonn,nice,more %O A051758 2,2 %A A051758 Robert Trent (trentrd(AT)hotmail.com), Aug 23 2000 %E A051758 a(9) from _Sean A. Irvine_, Oct 05 2021