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 A187519 #6 Jul 22 2025 10:47:35 %S A187519 113,1590,34776,1655170,144075566 %N A187519 Number of (n+1)X(n+1) 0..4 arrays with the array of 2X2 subblock determinants antisymmetric and no off-diagonal 2X2 subblock determinant zero. %C A187519 Column 4 of A187521 %e A187519 Some solutions for 4X4 %e A187519 ..0..3..1..1....1..1..1..2....0..3..1..2....1..1..3..1....2..2..3..2 %e A187519 ..0..1..1..2....1..1..3..0....0..1..1..4....2..2..2..2....2..2..4..1 %e A187519 ..2..1..1..0....3..1..3..2....2..1..1..2....0..2..2..1....2..1..2..2 %e A187519 ..3..1..3..0....0..2..0..0....2..0..2..4....2..3..4..2....3..4..2..2 %K A187519 nonn %O A187519 1,1 %A A187519 _R. H. Hardin_ Mar 10 2011