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 A180751 #5 Jul 22 2025 08:28:06 %S A180751 0,1,1,9,86,2986,205020,33329847,11843513563,9371551715962, %T A180751 16360949033733903 %N A180751 Half the number of n X n binary arrays with each element equal to at least two neighbors. %C A180751 Diagonal of A180760 %K A180751 nonn %O A180751 1,4 %A A180751 _R. H. Hardin_ Sep 20 2010