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A258731 Number of length n+1 0..3 arrays with at most one downstep in every n consecutive neighbor pairs. 1
16, 60, 190, 512, 1212, 2592, 5115, 9460, 16588, 27820, 44928, 70240, 106760, 158304, 229653, 326724, 456760, 628540, 852610, 1141536, 1510180, 1976000, 2559375, 3283956, 4177044, 5269996, 6598660, 8203840, 10131792, 12434752, 15171497 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Row 1 of A258730.

LINKS

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

FORMULA

Empirical: a(n) = (1/5040)*n^7 + (1/144)*n^6 + (73/720)*n^5 + (91/144)*n^4 + (179/90)*n^3 + (139/36)*n^2 + (568/105)*n + 4.

Empirical g.f.: x*(2 - x)*(8 - 30*x + 64*x^2 - 80*x^3 + 58*x^4 - 23*x^5 + 4*x^6) / (1 - x)^8. - Colin Barker, Jan 26 2018

EXAMPLE

Some solutions for n=4:

..3....1....0....1....0....0....2....1....3....0....0....1....1....1....3....3

..3....3....1....2....0....0....3....2....0....2....2....2....1....1....0....3

..2....3....0....2....0....0....1....0....0....0....2....3....2....1....1....1

..2....1....3....2....2....2....2....1....1....0....3....1....3....3....1....3

..2....1....3....2....1....2....3....1....1....1....3....2....3....0....2....3

CROSSREFS

Cf. A258730.

Sequence in context: A258730 A187173 A296958 * A316125 A039406 A031190

Adjacent sequences:  A258728 A258729 A258730 * A258732 A258733 A258734

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jun 08 2015

STATUS

approved

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Last modified February 19 13:23 EST 2020. Contains 332044 sequences. (Running on oeis4.)