A264622 Number of (n+1) X (1+1) arrays of permutations of 0..n*2+1 with each element having directed index change -2,0 -1,0 0,-1 or 1,1.

0, 1, 2, 1, 1, 4, 6, 5, 7, 15, 21, 23, 34, 58, 80, 101, 149, 230, 319, 431, 629, 928, 1299, 1810, 2617, 3784, 5336, 7536, 10828, 15521, 21992, 31236, 44713, 63862, 90741, 129177, 184524, 263178, 374521, 533619, 761403, 1085401, 1545839, 2203162

Offset: 1

Author

R. H. Hardin, Nov 19 2015

Keywords

• nonn

Examples

			All solutions for n=4:
..1..5
..3..0
..8..2
..7..4
..9..6
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..210

Crossrefs

Column 1 of A264628.

Formula

Empirical: a(n) = a(n-3) + 2*a(n-4) + a(n-5).

Empirical g.f.: x^2*(1 + x)^2 / (1 - x^3 - 2*x^4 - x^5). - Colin Barker, Jan 08 2019