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 A264642 #3 Nov 19 2015 13:53:11 %S A264642 1,8,149,3741,199456,18120064,1726126592 %N A264642 Number of nX3 arrays of permutations of 0..n*3-1 with rows nondecreasing modulo 3 and columns nondecreasing modulo 4. %C A264642 Column 3 of A264643. %e A264642 Some solutions for n=4 %e A264642 ..4.10..8....2..8..5....4..5..8....9..6..0....4..5..8....1..5..8....1..8..5 %e A264642 ..0..7..1....6..0..9....6..9..0....1.10..4....6..9..0....9..6..0....6..0..9 %e A264642 ..6..3..9....3..4..1...10..1..7...11..2..8....3..1.10...10..7..4....7..4.10 %e A264642 ..2.11..5....7.10.11....3..2.11....3..7..5....7..2.11....3.11..2....3.11..2 %Y A264642 Cf. A264643. %K A264642 nonn %O A264642 1,2 %A A264642 _R. H. Hardin_, Nov 19 2015