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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.

A203649 1/25 the number of (n+1) X (n+1) 0..4 arrays with every 2 X 2 subblock having equal diagonal elements or equal antidiagonal elements.

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%I A203649 #8 Feb 22 2025 14:34:24
%S A203649 9,1517,1116249,3906948333,67213191427593,5796397762880763341
%N A203649 1/25 the number of (n+1) X (n+1) 0..4 arrays with every 2 X 2 subblock having equal diagonal elements or equal antidiagonal elements.
%e A203649 Some solutions for n=4:
%e A203649 ..0..1..2..2..4....0..2..2..0..0....1..1..4..3..2....3..3..0..3..4
%e A203649 ..2..0..1..2..2....4..0..2..2..0....2..1..1..4..3....2..3..3..4..1
%e A203649 ..3..2..0..1..2....3..4..0..2..2....0..2..1..1..4....3..3..0..3..4
%e A203649 ..1..3..2..0..1....0..3..4..0..2....0..0..2..1..1....3..2..3..2..3
%e A203649 ..0..1..3..2..0....3..0..3..4..0....3..0..0..2..1....4..3..0..3..0
%Y A203649 Diagonal of A203656.
%K A203649 nonn,more
%O A203649 1,1
%A A203649 _R. H. Hardin_, Jan 04 2012

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