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 A189257 #9 Jul 22 2025 11:38:24 %S A189257 2,16,280,8900,552752,68635317,17747766886,9421503162646, %T A189257 10606582683139102,24593238398265693575,121227430181311808878846, %U A189257 1234571538047080619811567488,26705899629138438568650919545084 %N A189257 Number of n X n binary arrays without the pattern 0 0 1 diagonally, antidiagonally or horizontally. %C A189257 Diagonal of A189264 %H A189257 R. H. Hardin, <a href="/A189257/b189257.txt">Table of n, a(n) for n = 1..15</a> %e A189257 Some solutions for 3X3 %e A189257 ..0..1..1....1..0..1....1..1..0....1..1..0....1..1..0....1..1..1....0..1..1 %e A189257 ..1..1..0....1..0..1....1..0..1....0..0..0....0..1..1....0..0..0....0..1..1 %e A189257 ..1..1..1....0..1..0....0..1..1....0..0..0....1..0..0....1..1..0....1..1..0 %K A189257 nonn %O A189257 1,1 %A A189257 _R. H. Hardin_ Apr 19 2011