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A264507 Number of (1+1) X (n+1) arrays of permutations of 0..n*2+1 with each element having directed index change -1,1 0,-1 0,1 or 1,0. 1
1, 1, 3, 6, 12, 24, 46, 91, 177, 349, 684, 1345, 2640, 5185, 10180, 19989, 39249, 77067, 151326, 297136, 583444, 1145622, 2249491, 4416993, 8673001, 17029896, 33439105, 65659456, 128925825, 253152696, 497078745, 976040481, 1916507251, 3763163638 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

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

FORMULA

Empirical: a(n) = 2*a(n-1) + a(n-2) - 3*a(n-3) + a(n-4) + 2*a(n-5) - a(n-6).

Empirical g.f.: x*(1 - x + 2*x^3 - x^4) / (1 - 2*x - x^2 + 3*x^3 - x^4 - 2*x^5 + x^6). - Colin Barker, Jan 08 2019

EXAMPLE

Some solutions for n=4:

..1..2..3..7..8....1..5..3..2..8....1..5..6..2..3....1..5..6..4..3

..0..5..6..9..4....0..7..6..9..4....0..7..8..9..4....0..7..2..9..8

CROSSREFS

Row 1 of A264506.

Sequence in context: A018183 A196787 A200662 * A137711 A068032 A293341

Adjacent sequences:  A264504 A264505 A264506 * A264508 A264509 A264510

KEYWORD

nonn

AUTHOR

R. H. Hardin, Nov 15 2015

STATUS

approved

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Last modified September 20 14:44 EDT 2021. Contains 347586 sequences. (Running on oeis4.)