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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.

A187459 Number of (n+1)X(n+1) 0..2 arrays with all the 2X2 subblocks nonsingular and the array of 2X2 subblock determinants symmetric.

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%I A187459 #6 Jul 22 2025 10:46:02
%S A187459 50,1236,89618,11684688,6112320620,4871877392202,17264863350746654,
%T A187459 83050637417670542044
%N A187459 Number of (n+1)X(n+1) 0..2 arrays with all the 2X2 subblocks nonsingular and the array of 2X2 subblock determinants symmetric.
%C A187459 Column 2 of A187462
%e A187459 Some solutions for 4X4
%e A187459 ..2..2..2..0....1..1..1..2....1..1..2..0....2..1..2..2....0..2..0..2
%e A187459 ..1..2..0..2....0..2..0..1....2..1..0..2....1..2..1..0....2..0..2..2
%e A187459 ..2..0..1..1....1..0..2..2....2..0..1..0....2..1..2..2....0..2..1..2
%e A187459 ..2..2..2..0....2..1..2..0....2..2..2..2....2..0..2..0....2..2..2..0
%K A187459 nonn
%O A187459 1,1
%A A187459 _R. H. Hardin_ Mar 10 2011

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