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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.

A187627 Number of 5X5 0..n 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 A187627 #6 Jul 22 2025 10:50:42
%S A187627 948,324452,12278892,221177664,1896404966
%N A187627 Number of 5X5 0..n arrays with each 2X2 non-center subblock determinant nonzero and the array of 2X2 subblock determinants antisymmetric under 90 degree rotation.
%C A187627 Row 4 of A187624
%e A187627 Some n=3 solutions for 5X5
%e A187627 ..2..0..3..0..2....1..0..3..0..1....1..0..1..1..2....1..0..3..0..1
%e A187627 ..0..2..3..2..3....0..2..0..2..0....0..2..0..2..2....0..2..1..2..1
%e A187627 ..3..0..3..0..3....3..2..3..0..3....1..0..1..0..1....3..0..2..0..3
%e A187627 ..1..2..0..2..1....0..2..0..2..0....0..2..1..2..2....0..2..0..2..2
%e A187627 ..2..0..3..2..3....1..1..3..3..1....1..2..2..2..3....1..0..3..1..2
%K A187627 nonn
%O A187627 1,1
%A A187627 _R. H. Hardin_ Mar 12 2011

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