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A189436
Number of 4 X n array permutations with each element not moving, or moving one space N, SW or SE.
1
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
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
KEYWORD
nonn
AUTHOR
R. H. Hardin, Apr 22 2011
STATUS
approved