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A255109 Number of length n+2 0..2 arrays with at most one downstep in every n consecutive neighbor pairs. 1
27, 75, 168, 331, 597, 1008, 1616, 2484, 3687, 5313, 7464, 10257, 13825, 18318, 23904, 30770, 39123, 49191, 61224, 75495, 92301, 111964, 134832, 161280, 191711, 226557, 266280, 311373, 362361, 419802, 484288, 556446, 636939, 726467, 825768, 935619 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Row 2 of A255107.

LINKS

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

FORMULA

Empirical: a(n) = (1/120)*n^5 + (5/24)*n^4 + (37/24)*n^3 + (175/24)*n^2 + (239/20)*n + 6.

Empirical g.f.: x*(3 - 3*x + x^2)*(9 - 20*x + 18*x^2 - 6*x^3) / (1 - x)^6. - Colin Barker, Jan 24 2018

EXAMPLE

Some solutions for n=4:

0   2   2   0   2   2   1   0   0   1   1   1   1   2   2   2

0   2   0   1   0   2   1   0   2   1   0   1   1   1   0   2

0   1   2   0   1   2   1   0   0   2   0   2   0   1   1   0

1   1   2   1   2   0   0   2   0   1   0   2   0   1   1   0

0   1   2   2   2   2   1   2   0   1   2   1   1   1   2   0

1   1   2   2   2   2   2   2   1   2   1   2   1   2   2   1

CROSSREFS

Cf. A255107.

Sequence in context: A325824 A163506 A226357 * A297326 A044165 A044546

Adjacent sequences:  A255106 A255107 A255108 * A255110 A255111 A255112

KEYWORD

nonn

AUTHOR

R. H. Hardin, Feb 14 2015

STATUS

approved

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Last modified October 21 09:09 EDT 2020. Contains 337911 sequences. (Running on oeis4.)