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A222549 Number of (n+2) X 1 arrays of occupancy after each element moves up to +-2 places but not 0. 1
7, 20, 64, 208, 651, 2056, 6496, 20483, 64627, 203905, 643272, 2029453, 6402679, 20199560, 63726952, 201050056, 634285971, 2001087460, 6313163200, 19917184799, 62836052203, 198239333473, 625418559696, 1973111833705, 6224903700199 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 2 of A222555.

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..147

FORMULA

Empirical: a(n) = 5*a(n-1) - 6*a(n-2) + 2*a(n-3) - 8*a(n-4) + 12*a(n-5) - 3*a(n-6) - a(n-7).

Empirical g.f.: x*(7 - 15*x + 6*x^2 - 6*x^3 + 11*x^4 - 3*x^5 - x^6) / ((1 - x)*(1 - 4*x + 2*x^2 + 8*x^4 - 4*x^5 - x^6)). - Colin Barker, Aug 16 2018

EXAMPLE

Some solutions for n=3:

..0....0....0....0....2....0....0....1....0....1....0....1....2....2....1....1

..3....1....2....2....0....1....1....1....0....2....0....1....2....1....0....2

..2....4....1....1....2....2....3....0....3....0....1....0....0....1....1....1

..0....0....2....1....1....0....0....2....1....2....2....1....1....1....1....0

..0....0....0....1....0....2....1....1....1....0....2....2....0....0....2....1

CROSSREFS

Cf. A222555.

Sequence in context: A218843 A219422 A209546 * A196584 A301777 A299181

Adjacent sequences:  A222546 A222547 A222548 * A222550 A222551 A222552

KEYWORD

nonn

AUTHOR

R. H. Hardin, Feb 24 2013

STATUS

approved

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Last modified March 31 16:44 EDT 2020. Contains 333151 sequences. (Running on oeis4.)