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A264218 Number of (1+1) X (n+1) arrays of permutations of 0..n*2+1 with each element having directed index change 0,0 0,1 1,0 -1,0 or 0,-2. 1
4, 17, 56, 172, 561, 1826, 5880, 18993, 61424, 198472, 641297, 2072482, 6697372, 21642593, 69939048, 226011412, 730364961, 2360204994, 7627103920, 24647309729, 79648825312, 257388562256, 831762066401, 2687874415810, 8685980265204 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = 2*a(n-1) + 2*a(n-2) + 6*a(n-3) + 2*a(n-4) - 2*a(n-5) - a(n-6).
Empirical g.f.: x*(4 + 9*x + 14*x^2 + 2*x^3 - 5*x^4 - 2*x^5) / (1 - 2*x - 2*x^2 - 6*x^3 - 2*x^4 + 2*x^5 + x^6). - Colin Barker, Jan 06 2019
EXAMPLE
Some solutions for n=4:
..0..1..4..2..9....5..6..1..2..9....0..3..1..2..4....5..1..4..2..3
..5..6..7..3..8....0..8..7..3..4....5..8..6..7..9....0..6..7..8..9
CROSSREFS
Row 1 of A264217.
Sequence in context: A108140 A213577 A255526 * A121327 A317757 A183924
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 08 2015
STATUS
approved

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Last modified May 27 06:20 EDT 2024. Contains 372848 sequences. (Running on oeis4.)