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 A264558 #3 Nov 17 2015 18:04:25 %S A264558 1,3,15,156,2032,30912,737280,19491840,585019584,26539425792, %T A264558 1275815411712,65050879721472 %N A264558 Number of nX2 arrays of permutations of 0..n*2-1 with rows nondecreasing modulo 2 and columns nondecreasing modulo 3. %C A264558 Column 2 of A264560. %e A264558 Some solutions for n=4 %e A264558 ..0..7....6..1....6..3....6..3....0..6....0..6....6..4....6..3....0..3....6..3 %e A264558 ..6..4....3..7....0..7....0..1....4..3....7..3....3..7....0..1....6..1....0..4 %e A264558 ..3..1....0..5....4..1....2..4....5..1....2..4....0..2....4..7....7..5....1..7 %e A264558 ..2..5....4..2....2..5....5..7....2..7....5..1....1..5....2..5....4..2....2..5 %Y A264558 Cf. A264560. %K A264558 nonn %O A264558 1,2 %A A264558 _R. H. Hardin_, Nov 17 2015