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 A187460 #6 Jul 22 2025 10:46:09 %S A187460 192,13726,5098224,3387715318,19708386669940,150657364854061134 %N A187460 Number of (n+1)X(n+1) 0..3 arrays with all the 2X2 subblocks nonsingular and the array of 2X2 subblock determinants symmetric. %C A187460 Column 3 of A187462 %e A187460 Some solutions for 5X5 %e A187460 ..0..2..2..0..1....0..2..2..0..1....0..2..2..0..1....0..2..2..0..2 %e A187460 ..2..2..0..2..1....2..2..0..2..0....2..2..0..2..1....2..2..0..2..2 %e A187460 ..2..0..1..0..1....2..0..3..0..2....2..0..3..0..3....2..0..2..0..1 %e A187460 ..0..2..0..1..3....0..2..0..2..1....0..2..0..2..1....0..2..0..2..0 %e A187460 ..1..2..1..2..3....1..2..2..1..0....1..1..3..3..3....2..1..1..3..1 %K A187460 nonn %O A187460 1,1 %A A187460 _R. H. Hardin_ Mar 10 2011