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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.

A187672 Number of 4X4 0..n arrays with each 2X2 subblock nonsingular and the array of 2X2 subblock determinants symmetric about the diagonal and antidiagonal.

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%I A187672 #6 Jul 22 2025 10:52:17
%S A187672 112,11282,174292,1549398,6839146,32368980,88344978,268011840
%N A187672 Number of 4X4 0..n arrays with each 2X2 subblock nonsingular and the array of 2X2 subblock determinants symmetric about the diagonal and antidiagonal.
%C A187672 Row 3 of A187670
%e A187672 Some n=3 solutions for 4X4
%e A187672 ..0..1..1..2....0..2..2..2....0..2..2..3....0..2..2..2....2..1..1..2
%e A187672 ..2..0..2..3....2..0..3..0....2..0..2..1....3..0..3..1....1..0..2..2
%e A187672 ..3..1..0..1....2..3..0..2....0..2..0..2....0..2..0..2....2..2..0..1
%e A187672 ..1..0..2..1....2..0..2..1....2..2..2..1....2..1..3..3....3..2..1..3
%K A187672 nonn
%O A187672 1,1
%A A187672 _R. H. Hardin_ Mar 12 2011

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