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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.

A187696 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 horizontal and vertical reflection.

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%I A187696 #7 Jul 22 2025 10:52:39
%S A187696 6,0,104,0,9350,0,4280018,0,9966761956,0,118224466422070,0,
%T A187696 7149599148533804130,0,2205540801307910506482568,0
%N A187696 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 horizontal and vertical reflection.
%C A187696 Column 1 of A187699
%e A187696 Some solutions for 4X4
%e A187696 ..1..0..1..1....1..1..0..1....1..1..1..1....1..1..0..1....0..1..0..1
%e A187696 ..1..1..0..1....1..0..1..1....1..0..1..0....1..0..1..0....1..0..1..0
%e A187696 ..1..0..1..0....0..1..0..1....1..1..0..1....0..1..0..1....0..1..0..1
%e A187696 ..1..1..0..1....1..0..1..1....1..0..1..0....1..1..1..0....1..1..1..0
%K A187696 nonn
%O A187696 1,1
%A A187696 _R. H. Hardin_ Mar 12 2011

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