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 A206988 #8 Jul 22 2025 19:53:51 %S A206988 2,16,174,6510,516724,88819714,37849652838,36679559167444, %T A206988 82039130470188394,429029852979061855882,5194153238714571994969836, %U A206988 145816870651378340099973452074 %N A206988 Number of n X n 0..1 arrays avoiding 0 0 0 horizontally and 1 1 1 vertically. %C A206988 Diagonal of A206994 %e A206988 Some solutions for n=4 %e A206988 ..1..1..1..1....1..0..1..0....1..0..0..1....1..0..1..0....0..1..0..1 %e A206988 ..1..1..0..1....1..1..0..1....0..1..1..0....1..0..0..1....1..1..1..0 %e A206988 ..0..0..1..0....0..1..0..0....1..0..1..1....0..1..0..0....0..0..1..0 %e A206988 ..1..1..1..0....1..0..1..0....1..1..0..1....0..1..0..0....0..1..0..1 %K A206988 nonn %O A206988 1,1 %A A206988 _R. H. Hardin_ Feb 14 2012