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 A187518 #6 Jul 22 2025 10:47:28 %S A187518 64,450,4200,73764,2048596,129034386,13881494364 %N A187518 Number of (n+1)X(n+1) 0..3 arrays with the array of 2X2 subblock determinants antisymmetric and no off-diagonal 2X2 subblock determinant zero. %C A187518 Column 3 of A187521 %e A187518 Some solutions for 4X4 %e A187518 ..0..0..1..0....0..1..0..1....2..2..2..3....3..2..3..3....2..2..3..2 %e A187518 ..2..2..2..1....0..3..3..2....2..2..1..0....3..2..1..3....2..2..1..2 %e A187518 ..2..3..3..3....1..1..1..1....1..2..1..3....1..2..1..1....0..2..1..1 %e A187518 ..1..1..0..0....0..3..2..2....0..3..0..0....3..0..1..1....2..3..2..2 %K A187518 nonn %O A187518 1,1 %A A187518 _R. H. Hardin_ Mar 10 2011