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A264629
Number of (2+1) X (n+1) arrays of permutations of 0..n*3+2 with each element having directed index change -2,0 -1,0 0,-1 or 1,1.
1
1, 2, 4, 9, 16, 37, 76, 160, 337, 704, 1485, 3110, 6532, 13713, 28784, 60441, 126872, 266368, 559201, 1173968, 2464617, 5174122, 10862468, 22804377, 47874976, 100507613, 211003236, 442975264, 929971633, 1952360368, 4098738901
OFFSET
1,2
LINKS
FORMULA
Empirical: a(n) = 2*a(n-1) + 2*a(n-5) - 2*a(n-6) + 4*a(n-7) - a(n-10).
Empirical g.f.: x*(1 + x^3 - 2*x^4 + 3*x^5 - x^8) / (1 - 2*x - 2*x^5 + 2*x^6 - 4*x^7 + x^10). - Colin Barker, Jan 08 2019
EXAMPLE
Some solutions for n=4:
..1..6..3..4..9....1..6..7..4..9...10..2.12..4.14....5..2..7..4..9
.10..0.12..2.14...10..0.12..2..3....6..0..1..9..3...10..0..1.13..3
.11..5.13..7..8...11..5.13.14..8...11..5.13..7..8...11.12..6.14..8
CROSSREFS
Row 2 of A264628.
Sequence in context: A203318 A282776 A283015 * A349328 A358904 A283059
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 19 2015
STATUS
approved