A189436 Number of 4 X n array permutations with each element not moving, or moving one space N, SW or SE.

1, 9, 31, 140, 571, 2413, 10069, 42205, 176624, 739573, 3096173, 12962845, 54270579, 227212636, 951259751, 3982596009, 16673747193, 69807202249, 292258553696, 1223585260409, 5122727328297, 21447083573633, 89791504401207

Offset

1,2

Comments

Row 4 of A189435.

Links

R. H. Hardin, Table of n, a(n) for n = 1..200

Formula

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

Empirical g.f.: x*(1 + 5*x - 7*x^2 + 4*x^3 - x^4) / (1 - 4*x - 2*x^2 + 6*x^3 - 4*x^4 + x^5). - Colin Barker, May 02 2018

Example

Some solutions for 4 X 3:
..0..1..5....0..1..2....0..4..5....3..4..2....0..4..5....0..4..5....0..4..5
..6..2..8....3..4..5....3..2..1....1..0..5....3..2..1....6..2..1....1..2..8
..4..3.11....9.10..8....9.10..8....6..7..8....6.10.11....9..3..8....6..3.11
..9.10..7....7..6.11....7..6.11....9.10.11....9..8..7....7.10.11....9.10..7

Crossrefs

Cf. A189435.

Sequence in context: A184054 A140323 A160653 * A145950 A177743 A266710

Adjacent sequences: A189433 A189434 A189435 * A189437 A189438 A189439

Keyword

nonn

Author

R. H. Hardin, Apr 22 2011

Status

approved