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 A187703 #6 Jan 20 2024 16:41:25 %S A187703 113,31461,1718,875696,4612 %N A187703 Number of (n+1) X (n+1) 0..4 arrays with each 2 X 2 subblock off diagonal and antidiagonal nonsingular and the array of 2 X 2 subblock determinants antisymmetric about the diagonal and antidiagonal. %C A187703 Column 4 of A187705. %e A187703 Some solutions for 4 X 4 %e A187703 ..0..2..1..1....0..0..1..0....2..2..4..2....0..3..0..0....4..3..4..4 %e A187703 ..0..1..1..1....3..2..1..0....2..2..2..1....0..1..1..2....4..3..3..3 %e A187703 ..1..1..1..0....2..2..1..2....2..4..4..4....3..3..3..3....3..3..3..4 %e A187703 ..3..3..4..0....4..4..1..2....2..4..3..3....0..0..1..1....1..1..0..0 %Y A187703 Cf. A187705. %K A187703 nonn %O A187703 1,1 %A A187703 _R. H. Hardin_, Mar 12 2011