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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.

A187525 Number of (n+1)X(n+1) 0..1 arrays with each 2X2 subblock determinant nonzero and the array of 2X2 subblock determinants symmetric under 90 degree rotation.

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%I A187525 #7 Jul 22 2025 10:48:11
%S A187525 6,0,104,0,9346,0,4278774,0,9966039904,0,118222727145122,0,
%T A187525 7149579817467705382,0,2205539783282634028931328
%N A187525 Number of (n+1)X(n+1) 0..1 arrays with each 2X2 subblock determinant nonzero and the array of 2X2 subblock determinants symmetric under 90 degree rotation.
%C A187525 Column 1 of A187528
%e A187525 Some solutions for 4X4
%e A187525 ..0..1..0..1....1..1..0..1....1..0..1..1....1..0..1..0....1..1..0..1
%e A187525 ..1..0..1..0....1..0..1..0....0..1..0..1....0..1..0..1....1..0..1..1
%e A187525 ..0..1..1..1....0..1..0..1....1..0..1..0....1..1..1..0....1..1..0..1
%e A187525 ..1..0..1..0....1..1..1..1....0..1..1..1....0..1..0..1....1..0..1..0
%K A187525 nonn
%O A187525 1,1
%A A187525 _R. H. Hardin_ Mar 10 2011

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