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 A231256 #6 Jul 23 2025 06:20:48 %S A231256 2,15,304,19503,3130708,1350570015,1496478177166,4339950773804841, %T A231256 32510127329051575349,631327524382609726232392, %U A231256 31694391041907948471880253567 %N A231256 Number of (n+1)X(n+1) 0..2 arrays with no element unequal to a strict majority of its horizontal and antidiagonal neighbors, with values 0..2 introduced in row major order. %C A231256 Diagonal of A231263 %e A231256 Some solutions for n=3 %e A231256 ..0..0..0..0....0..0..1..1....0..0..1..1....0..0..0..0....0..0..0..1 %e A231256 ..1..1..1..1....0..1..1..2....0..1..1..2....1..1..0..0....0..0..1..0 %e A231256 ..2..2..2..2....2..2..2..0....1..2..2..0....1..2..2..0....1..1..0..2 %e A231256 ..1..1..1..1....2..2..0..0....2..2..0..0....2..2..0..0....0..0..2..2 %K A231256 nonn %O A231256 1,1 %A A231256 _R. H. Hardin_, Nov 06 2013