cp's OEIS Frontend

A215290 Number of permutations of 0..floor((n*6-1)/2) on even squares of an nX6 array such that each row and column of even squares is increasing.

%I A215290 #6 Jul 22 2025 23:23:35
%S A215290 1,20,420,23100,1051050,85765680,5703417720,577185873264,
%T A215290 48236247979920,5595404765670720,545152292883918720,
%U A215290 69506917342699636800,7562187114225380722800,1033498905610802032116000
%N A215290 Number of permutations of 0..floor((n*6-1)/2) on even squares of an nX6 array such that each row and column of even squares is increasing.
%C A215290 Column 6 of A215292
%H A215290 R. H. Hardin, <a href="/A215290/b215290.txt">Table of n, a(n) for n = 1..210</a>
%F A215290 f3=floor((n+1)/2)
%F A215290 f4=floor(n/2)
%F A215290 a(n) = A060854(3,f3)*A060854(3,f4)*binomial(3*f3+3*f4,3*f3)
%e A215290 Some solutions for n=4
%e A215290 ..0..x..2..x..6..x....1..x..6..x..7..x....1..x..2..x..7..x....0..x..2..x..6..x
%e A215290 ..x..1..x..3..x..5....x..0..x..2..x..4....x..0..x..4..x.10....x..3..x..5..x..7
%e A215290 ..4..x..9..x.10..x....9..x.10..x.11..x....3..x..6..x..8..x....1..x..9..x.11..x
%e A215290 ..x..7..x..8..x.11....x..3..x..5..x..8....x..5..x..9..x.11....x..4..x..8..x.10
%K A215290 nonn
%O A215290 1,2
%A A215290 _R. H. Hardin_ Aug 07 2012