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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.

A203828 Number of (n+1)X(n+1) 0..2 arrays with every 2X2 subblock having equal diagonal elements or equal antidiagonal elements.

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%I A203828 #7 Jul 22 2025 17:32:26
%S A203828 45,1971,270333,119606211,173185290765,827309554361235,
%T A203828 13102412661293146461,690154670186627261773347
%N A203828 Number of (n+1)X(n+1) 0..2 arrays with every 2X2 subblock having equal diagonal elements or equal antidiagonal elements.
%C A203828 Diagonal of A203835
%e A203828 Some solutions for n=4
%e A203828 ..2..2..1..2..2....2..1..0..2..1....0..1..2..2..0....0..0..0..1..2
%e A203828 ..2..1..2..1..2....2..2..1..0..2....0..0..1..2..2....1..0..2..0..1
%e A203828 ..1..2..1..1..1....1..2..2..1..0....2..0..0..1..2....2..1..0..0..0
%e A203828 ..1..1..0..1..2....0..1..2..2..1....0..2..0..0..1....2..2..1..0..0
%e A203828 ..1..2..1..1..1....0..0..1..2..2....0..0..2..0..0....1..2..2..1..0
%K A203828 nonn
%O A203828 1,1
%A A203828 _R. H. Hardin_ Jan 06 2012

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