A264423 Number of (2+1) X (n+1) arrays of permutations of 0..n*3+2 with each element having directed index change 0,1 2,2 1,0 -1,2 -2,-1 or -1,-1.

1, 3, 12, 37, 119, 385, 1252, 4061, 13166, 42687, 138419, 448847, 1455443, 4719435, 15303308, 49622768, 160907641, 521761825, 1691873630, 5486097814, 17789312907, 57683924784, 187046863084, 606521298870, 1966716147754, 6377306803896

Offset: 1

Author

R. H. Hardin, Nov 12 2015

Keywords

• nonn

Examples

			Some solutions for n=4:
..6..7..1..2..3....6..0..1..9..3....6.12.13.14..7...11.12.13..2..3
..0.12.13.14..4...11.12..2.14..4....0..1..2..3..4....0..1..6.14..4
..5.10.11..8..9....5.10..7..8.13....5.10.11..8..9....5.10..7..8..9
		

Links

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

Crossrefs

Row 2 of A264422.

Formula

Empirical: a(n) = 3*a(n-1) + a(n-3) + 5*a(n-4) + a(n-7).

Empirical g.f.: x*(1 + 3*x^2 + x^5) / ((1 + x^2 + x^3)*(1 - 3*x - x^2 + x^3 - x^4)). - Colin Barker, Jan 07 2019