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 A356975 #8 Sep 07 2022 08:13:24 %S A356975 0,0,0,1,3,28,199,1603,12234,93270,697641,5167477,37913465 %N A356975 a(n) is the number of n-celled pseudo-polyominoes with holes. %e A356975 a(4)=1 because of: %e A356975 O %e A356975 O O %e A356975 O %e A356975 a(5)=3 because of: %e A356975 O O O %e A356975 O O O OO O O %e A356975 OO O O O %Y A356975 Cf. A030222, A001419. %K A356975 nonn,hard,more %O A356975 1,5 %A A356975 _John Mason_, Sep 07 2022