A264018 Number of (2+1) X (n+1) arrays of permutations of 0..n*3+2 with each element having index change +-(.,.) 0,0 1,2 or 2,2.

1, 5, 25, 105, 441, 1869, 7921, 33553, 142129, 602069, 2550409, 10803705, 45765225, 193864605, 821223649, 3478759201, 14736260449, 62423800997, 264431464441, 1120149658761, 4745030099481, 20100270056685, 85146110326225

Offset: 1

Author

R. H. Hardin, Nov 01 2015

Keywords

• nonn

Examples

			Some solutions for n=4:
..7..1..2..3..4....0.13..9..3..4....0..8..9..3..4....7..1..9..3..4
.12..6..0..8..9...12..6..7..8..2...12..6.14..1..2...12.13..0..8..2
.10.11..5.13.14...10.11..5..1.14...10.11..5.13..7...10.11..5..6.14
		

Links

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

Crossrefs

Row 2 of A264017.

Formula

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

Empirical g.f.: x*(1 + x + 5*x^2 + x^3) / ((1 + x^2)*(1 - 4*x - x^2)). - Colin Barker, Jan 03 2019

Empirical: 5*a(n) = 2*A228826(n) + A048876(n). - R. J. Mathar, Sep 09 2020