A264491 Number of (2+1) X (n+1) arrays of permutations of 0..n*3+2 with each element having directed index change 2,-1 1,0 2,1 0,-1 -2,-2 or -1,0.

3, 1, 10, 8, 35, 42, 130, 194, 501, 849, 1979, 3613, 7942, 15145, 32182, 62953, 131165, 260426, 536438, 1074379, 2198378, 4425274, 9019904, 18210519, 37034259, 74898261, 152118445, 307953916, 624975597, 1265962640, 2568054807, 5203674585

Offset: 1

Author

R. H. Hardin, Nov 14 2015

Keywords

• nonn

Examples

			Some solutions for n=4:
.12..6..7..4..9....5..6.14..8..9...12..6..7..8..9....5..6.14..8..9
.10.11..2.13.14...10.11.12.13..4...10.11..2.13..4...10..7.12.13..4
..5..0..1..8..3....1..0..7..2..3....5..0..1.14..3...11..0..1..2..3
		

Links

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

Crossrefs

Row 2 of A264490.

Formula

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

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