A222549 Number of (n+2) X 1 arrays of occupancy after each element moves up to +-2 places but not 0.

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

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