A264380 Number of (2+1) X (n+1) arrays of permutations of 0..n*3+2 with each element having directed index change 2,-2 -1,0 -1,2 1,0 or 0,-1.

0, 1, 6, 9, 61, 121, 544, 1357, 5100, 14340, 49324, 147230, 485141, 1491460, 4812843, 15012153, 47950974, 150636184, 478755674, 1509249756, 4785018013, 15110309428, 47849311565, 151226992088, 478604645313, 1513243349293, 4787751445331

Offset: 1

Author

R. H. Hardin, Nov 12 2015

Keywords

• nonn

Examples

			Some solutions for n=4:
..1..6..5..4..7....1..2..3..8..7....5..6..3..8..7....5..2..3..8..7
..0.11.10..3.14....0.11.10.13.12....0..1.10.11..4....0..1.10.13.12
..2.12.13..8..9....5..6..4.14..9....2.12.13.14..9...11..6..4.14..9
		

Links

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

Crossrefs

Row 2 of A264379.

Formula

Empirical: a(n) = 2*a(n-1) + 5*a(n-2) - 6*a(n-3) + 7*a(n-4) - 4*a(n-5) - a(n-6) + 5*a(n-7) - 4*a(n-8) + 2*a(n-9) - a(n-10).

Empirical g.f.: x^2*(1 + 4*x - 8*x^2 + 19*x^3 - 17*x^4 + 13*x^5 - 8*x^6 + 2*x^7 - x^8) / (1 - 2*x - 5*x^2 + 6*x^3 - 7*x^4 + 4*x^5 + x^6 - 5*x^7 + 4*x^8 - 2*x^9 + x^10). - Colin Barker, Jan 07 2019