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A255108 Number of length n+1 0..2 arrays with at most one downstep in every n consecutive neighbor pairs. 1
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified December 2 10:39 EST 2020. Contains 338876 sequences. (Running on oeis4.)