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 A231133 #6 Jul 23 2025 06:16:26 %S A231133 1,9,308,27171,6794904,4509445997,8349491299560,41122867660973690, %T A231133 564457878709147238868,20611335365445954476620968, %U A231133 2097381737046509117354544061212,567772314049031950964995256826728363 %N A231133 Number of (n+1)X(n+1) black-square subarrays of 0..2 arrays with no element equal to a strict majority of its diagonal and antidiagonal neighbors, with values 0..2 introduced in row major order. %C A231133 Diagonal of A231137 %e A231133 Some solutions for n=4 %e A231133 ..x..0..x..1..x....x..0..x..1..x....x..0..x..0..x....x..0..x..0..x %e A231133 ..2..x..0..x..2....1..x..2..x..2....1..x..0..x..1....0..x..1..x..2 %e A231133 ..x..0..x..1..x....x..0..x..0..x....x..1..x..1..x....x..2..x..1..x %e A231133 ..1..x..0..x..0....2..x..1..x..2....0..x..2..x..0....1..x..2..x..1 %e A231133 ..x..2..x..1..x....x..0..x..1..x....x..2..x..2..x....x..0..x..0..x %K A231133 nonn %O A231133 1,2 %A A231133 _R. H. Hardin_, Nov 04 2013