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 A202806 #8 Jun 02 2025 07:28:31 %S A202806 1,3,32,1177,146300,60758779,83834499040,383108603365234, %T A202806 5786835759666959842,288547665952004154207686, %U A202806 47452156644340908611972658594,25719338921489550833572201554228792 %N A202806 Number of n X n nonnegative integer arrays with each row and column increasing from zero by 0, 1 or 2. %C A202806 Diagonal of A202812 %e A202806 Some solutions for n=4 %e A202806 ..0..0..0..0....0..0..0..0....0..0..0..0....0..0..0..0....0..0..0..0 %e A202806 ..0..0..0..0....0..0..0..0....0..0..0..1....0..0..0..2....0..0..1..2 %e A202806 ..0..0..0..0....0..0..0..2....0..0..2..2....0..1..2..2....0..0..1..3 %e A202806 ..0..1..1..1....0..0..1..2....0..2..2..2....0..1..3..3....0..2..3..5 %K A202806 nonn %O A202806 1,2 %A A202806 _R. H. Hardin_ Dec 24 2011