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A264245 Number of (1+1) X (n+1) arrays of permutations of 0..n*2+1 with each element having directed index change 0,0 1,1 0,-1 -1,1 or 0,-2. 1
2, 8, 21, 57, 164, 460, 1289, 3629, 10202, 28672, 80609, 226609, 637024, 1790792, 5034233, 14152073, 39783914, 111839432, 314399813, 883831849, 2484603092, 6984645780, 19635038321, 55197463509, 155169545554, 436208230272 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = 2*a(n-1) + a(n-2) + 4*a(n-3) - a(n-4) - a(n-6).
Empirical g.f.: x*(2 + 4*x + 3*x^2 - x^3 - x^4 - x^5) / (1 - 2*x - x^2 - 4*x^3 + x^4 + x^6). - Colin Barker, Jan 06 2019
EXAMPLE
Some solutions for n=4:
..1..5..2..7..4....0..1..6..3..4....1..2..6..7..4....2..5..6..4..8
..6..0..8..9..3....5..7..8..2..9....5..0..8..9..3....7..0..1..9..3
CROSSREFS
Row 1 of A264244.
Sequence in context: A109782 A237268 A216893 * A123044 A143229 A123285
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 09 2015
STATUS
approved

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Last modified May 19 08:07 EDT 2024. Contains 372666 sequences. (Running on oeis4.)