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 A188825 #6 Jul 22 2025 11:24:14 %S A188825 8,16,48,144,432,1296,3888,11664,34992,104976,314928,944784,2834352, %T A188825 8503056,25509168,76527504,229582512,688747536,2066242608,6198727824, %U A188825 18596183472,55788550416,167365651248,502096953744,1506290861232 %N A188825 Number of 3Xn binary arrays without the pattern 0 1 diagonally or antidiagonally. %C A188825 Row 3 of A188824 %F A188825 Empirical: a(n) = 3*a(n-1) for n>2 %e A188825 Some solutions for 3X3 %e A188825 ..1..1..0....1..1..1....1..1..1....1..1..1....1..0..1....1..1..1....1..0..1 %e A188825 ..0..0..1....1..1..0....1..1..1....0..0..0....0..1..0....1..1..0....0..1..0 %e A188825 ..0..0..0....1..0..1....0..0..1....0..0..0....1..0..1....1..0..0....0..0..0 %K A188825 nonn %O A188825 1,1 %A A188825 _R. H. Hardin_ Apr 11 2011