A264366 Number of (2+1) X (n+1) arrays of permutations of 0..n*3+2 with each element having directed index change 0,0 0,2 1,0 or -1,-2.

1, 6, 36, 120, 400, 1440, 5184, 18432, 65536, 233472, 831744, 2962176, 10549504, 37572864, 133818624, 476601600, 1697440000, 6045523200, 21531453696, 76685407488, 273119121664, 972728179968, 3464422799616, 12338724758784

Offset

1,2

Links

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

Formula

Empirical: a(n) = 3*a(n-1) + 6*a(n-3) + 4*a(n-4).

Empirical g.f.: x*(1 + 3*x + 18*x^2 + 6*x^3) / ((1 + 2*x^2)*(1 - 3*x - 2*x^2)). - Colin Barker, Jan 07 2019

Example

Some solutions for n=4:
..0..8..2..1..4....0..8..9..3..4....0..8..2..3..4....7..1..0..3..2
..5..6.14..3..7...12..1..2..6..7....5..1..7..6..9....5..6.14..8..4
.10.11.12.13..9....5.11.10.13.14...10.11.12.13.14...10.11.12.13..9

Crossrefs

Row 2 of A264364.

Sequence in context: A225262 A253652 A083374 * A061707 A253945 A331576

Adjacent sequences: A264363 A264364 A264365 * A264367 A264368 A264369

Keyword

nonn

Author

R. H. Hardin, Nov 12 2015

Status

approved