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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.

A187461 Number of (n+1)X(n+1) 0..4 arrays with all the 2X2 subblocks nonsingular and the array of 2X2 subblock determinants symmetric.

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%I A187461 #6 Jul 22 2025 10:46:16
%S A187461 512,84048,100936174,216668424092,7540469990506332
%N A187461 Number of (n+1)X(n+1) 0..4 arrays with all the 2X2 subblocks nonsingular and the array of 2X2 subblock determinants symmetric.
%C A187461 Column 4 of A187462
%e A187461 Some solutions for 4X4
%e A187461 ..0..1..1..2....0..1..0..2....0..1..2..1....0..1..0..4....0..1..0..2
%e A187461 ..1..0..1..4....1..0..1..0....1..0..2..0....1..0..1..0....1..0..1..3
%e A187461 ..1..1..1..0....1..1..0..3....1..2..3..1....4..1..4..3....0..1..1..2
%e A187461 ..2..4..0..1....3..1..3..1....2..2..4..3....4..0..3..1....2..1..0..3
%K A187461 nonn
%O A187461 1,1
%A A187461 _R. H. Hardin_ Mar 10 2011

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