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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.

A207420 Number of n X n 0..1 arrays avoiding 0 0 0 and 0 1 0 horizontally and 0 0 1 and 0 1 0 vertically.

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%I A207420 #8 Jul 22 2025 20:24:12
%S A207420 2,16,114,1521,55361,3892729,474552171,116947584576,59951676534906,
%T A207420 60921409199181129,121441530119384020545,483128923550195512221129,
%U A207420 3857404253001354057074186601,61418617253685924322130029824769
%N A207420 Number of n X n 0..1 arrays avoiding 0 0 0 and 0 1 0 horizontally and 0 0 1 and 0 1 0 vertically.
%C A207420 Diagonal of A207426
%e A207420 Some solutions for n=4
%e A207420 ..1..0..1..1....1..1..1..0....1..0..0..1....0..0..1..1....0..1..1..0
%e A207420 ..0..0..1..1....0..0..1..1....1..0..1..1....1..1..1..0....1..0..1..1
%e A207420 ..1..0..1..1....0..1..1..1....0..0..1..1....1..1..0..0....1..0..0..1
%e A207420 ..1..0..0..1....0..1..1..1....1..0..0..1....1..1..1..0....0..0..1..1
%K A207420 nonn
%O A207420 1,1
%A A207420 _R. H. Hardin_ Feb 17 2012

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