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.
%I A187527 #6 Jul 22 2025 10:48:25 %S A187527 192,74,35026,20554,164460556 %N A187527 Number of (n+1)X(n+1) 0..3 arrays with each 2X2 subblock determinant nonzero and the array of 2X2 subblock determinants symmetric under 90 degree rotation. %C A187527 Column 3 of A187528 %e A187527 Some solutions for 4X4 %e A187527 ..3..3..3..3....3..0..3..3....2..3..2..3....0..3..0..3....2..2..1..2 %e A187527 ..2..3..2..3....1..3..0..3....0..1..0..1....3..0..3..1....1..0..1..0 %e A187527 ..1..0..1..0....3..0..3..1....2..1..2..1....0..3..0..3....2..2..2..2 %e A187527 ..1..3..0..3....3..3..0..3....0..1..0..1....3..3..3..1....3..2..3..2 %K A187527 nonn %O A187527 1,1 %A A187527 _R. H. Hardin_ Mar 10 2011