A255108 Number of length n+1 0..2 arrays with at most one downstep in every n consecutive neighbor pairs.

9, 26, 66, 147, 294, 540, 927, 1507, 2343, 3510, 5096, 7203, 9948, 13464, 17901, 23427, 30229, 38514, 48510, 60467, 74658, 91380, 110955, 133731, 160083, 190414, 225156, 264771, 309752, 360624, 417945, 482307, 554337, 634698, 724090, 823251, 932958

Offset

1,1

Comments

Row 1 of A255107.

Links

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

Formula

Empirical: a(n) = (1/120)*n^5 + (1/6)*n^4 + (19/24)*n^3 + (11/6)*n^2 + (16/5)*n + 3.

Empirical g.f.: x*(9 - 28*x + 45*x^2 - 39*x^3 + 17*x^4 - 3*x^5) / (1 - x)^6. - Colin Barker, Jan 24 2018

Example

Some solutions for n=4:
..1....1....0....0....0....1....0....0....1....2....0....0....1....1....0....0
..1....2....0....0....0....1....1....1....1....1....2....2....2....0....0....0
..0....0....2....2....1....2....0....1....1....2....2....2....2....0....2....2
..0....2....1....0....1....2....0....2....1....2....2....1....0....0....2....0
..1....2....1....2....2....1....1....1....2....2....0....2....2....0....1....1

Crossrefs

Cf. A255107.

Sequence in context: A249275 A270695 A048468 * A048771 A055849 A235163

Adjacent sequences: A255105 A255106 A255107 * A255109 A255110 A255111

Keyword

nonn

Author

R. H. Hardin, Feb 14 2015

Status

approved