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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

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

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

Adjacent sequences:  A264242 A264243 A264244 * A264246 A264247 A264248

KEYWORD

nonn

AUTHOR

R. H. Hardin, Nov 09 2015

STATUS

approved

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Last modified July 24 11:17 EDT 2021. Contains 346273 sequences. (Running on oeis4.)