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 A269136 #8 Apr 20 2020 19:49:37 %S A269136 4,148,18556,8317996,14197016484,95884587957284,2621894498331024092, %T A269136 294433751149574057834796,137064853562490916405823252564, %U A269136 266206369700280385363973380215109284 %N A269136 Number of n X n 0..3 arrays with some element plus some horizontally, antidiagonally or vertically adjacent neighbor totalling three no more than once. %C A269136 Diagonal of A269143. %e A269136 Some solutions for n=3 %e A269136 ..2..2..3. .0..0..2. .2..1..1. .2..3..2. .0..0..1. .3..1..3. .0..1..3 %e A269136 ..3..2..3. .0..2..2. .0..0..1. .3..2..2. .1..1..3. .3..1..3. .3..1..3 %e A269136 ..3..2..2. .0..0..1. .1..1..1. .3..2..2. .0..2..2. .3..2..3. .1..3..1 %Y A269136 Cf. A269143. %K A269136 nonn %O A269136 1,1 %A A269136 _R. H. Hardin_, Feb 20 2016