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A255626 Number of length n+4 0..2 arrays with at most two downsteps in every n consecutive neighbor pairs. 1
243, 729, 2187, 5997, 14381, 30816, 60390, 110270, 190269, 313527, 497322, 764028, 1142238, 1668071, 2386683, 3354003, 4638716, 6324516, 8512653, 11324799, 14906259, 19429554, 25098404, 32152140, 40870575, 51579365, 64655892, 80535702 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Row 4 of A255622.

LINKS

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

FORMULA

Empirical: a(n) = (1/40320)*n^8 + (17/10080)*n^7 + (119/2880)*n^6 + (871/720)*n^5 + (71047/5760)*n^4 + (3599/1440)*n^3 + (56139/1120)*n^2 + (27661/280)*n + 45 for n>2.

Empirical g.f.: x*(243 - 1458*x + 4374*x^2 - 7854*x^3 + 8522*x^4 - 5193*x^5 + 1134*x^6 + 680*x^7 - 630*x^8 + 210*x^9 - 27*x^10) / (1 - x)^9. - Colin Barker, Jan 21 2018

EXAMPLE

Some solutions for n=4:

..0....0....1....0....0....2....2....0....1....0....2....1....1....2....2....0

..1....1....1....2....0....2....0....2....0....0....0....0....0....0....2....0

..2....1....2....2....0....0....2....1....0....1....1....1....2....0....0....0

..1....2....1....2....2....1....0....2....1....0....2....2....1....0....2....2

..2....2....1....0....2....1....2....0....1....0....2....0....1....2....0....2

..2....2....2....0....1....2....0....0....2....0....0....1....2....0....2....0

..2....2....2....2....1....0....1....0....2....1....0....2....2....1....2....2

..0....1....2....1....0....2....2....1....0....0....0....0....0....2....1....0

CROSSREFS

Cf. A255622.

Sequence in context: A067838 A255111 A331613 * A205049 A235540 A219132

Adjacent sequences:  A255623 A255624 A255625 * A255627 A255628 A255629

KEYWORD

nonn

AUTHOR

R. H. Hardin, Feb 28 2015

STATUS

approved

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Last modified December 2 09:52 EST 2020. Contains 338876 sequences. (Running on oeis4.)