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 A187523 #6 Jul 22 2025 10:48:04 %S A187523 2,354,4200,34776,107990,475370,978568,2790760,5647886,11787078, %T A187523 17703910,41527872,57261832 %N A187523 Number of 4X4 0..n arrays with the array of 2X2 subblock determinants antisymmetric and no off-diagonal 2X2 subblock determinant zero. %C A187523 Row 3 of A187521 %e A187523 Some solutions for 4X4 %e A187523 ..2..2..1..1....2..3..1..2....1..3..1..3....2..2..3..3....1..1..0..3 %e A187523 ..1..1..1..0....2..3..2..1....1..3..2..2....1..1..1..2....1..1..2..1 %e A187523 ..2..1..1..1....3..3..2..2....2..3..2..1....0..1..1..0....3..1..2..3 %e A187523 ..3..2..1..1....0..1..0..0....0..2..2..1....3..1..3..0....0..2..0..0 %K A187523 nonn %O A187523 1,1 %A A187523 _R. H. Hardin_ Mar 10 2011