A255109 - OEIS

A255109

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

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

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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 * A369063 A297326 A044165

Adjacent sequences: A255106 A255107 A255108 * A255110 A255111 A255112

KEYWORD

nonn

AUTHOR

R. H. Hardin, Feb 14 2015

STATUS

approved