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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.

A187621 Number of (n+1)X(n+1) 0..1 arrays with each 2X2 non-center subblock determinant nonzero and the array of 2X2 subblock determinants antisymmetric under 90 degree rotation.

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%I A187621 #7 Jul 22 2025 10:49:59
%S A187621 10,24,2,948,36,190972,3020,194618700,929380,1018751442652,1744283776,
%T A187621 27189851221308572,15262275217840
%N A187621 Number of (n+1)X(n+1) 0..1 arrays with each 2X2 non-center subblock determinant nonzero and the array of 2X2 subblock determinants antisymmetric under 90 degree rotation.
%C A187621 Column 1 of A187624
%e A187621 All solutions for 4X4
%e A187621 ..1..1..0..1....1..0..1..1
%e A187621 ..0..1..1..1....1..1..1..0
%e A187621 ..1..1..1..0....0..1..1..1
%e A187621 ..1..0..1..1....1..1..0..1
%K A187621 nonn
%O A187621 1,1
%A A187621 _R. H. Hardin_ Mar 12 2011

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