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A256818 Number of length n+3 0..1 arrays with at most two downsteps in every n consecutive neighbor pairs. 1
16, 32, 64, 128, 245, 442, 753, 1220, 1894, 2836, 4118, 5824, 8051, 10910, 14527, 19044, 24620, 31432, 39676, 49568, 61345, 75266, 91613, 110692, 132834, 158396, 187762, 221344, 259583, 302950, 351947, 407108, 469000, 538224, 615416, 701248 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Row 3 of A256816.

LINKS

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

FORMULA

Empirical: a(n) = (1/120)*n^5 + (1/12)*n^4 + (31/24)*n^3 - (31/12)*n^2 + (66/5)*n + 4.

Empirical g.f.: x*(16 - 64*x + 112*x^2 - 96*x^3 + 37*x^4 - 4*x^5) / (1 - x)^6. - Colin Barker, Jan 21 2018

EXAMPLE

Some solutions for n=4:

..0....1....1....1....1....1....1....0....0....1....0....1....0....1....1....0

..1....1....1....1....1....1....0....1....0....0....1....0....0....1....1....1

..1....1....1....1....1....1....1....0....1....1....0....0....0....0....0....0

..0....0....1....0....1....0....1....1....1....1....0....1....0....1....1....1

..1....0....0....1....1....1....0....1....1....1....1....0....1....0....0....0

..0....0....0....0....1....1....0....1....0....0....0....1....1....0....1....1

..0....1....0....1....1....1....0....0....0....1....0....1....0....0....0....0

CROSSREFS

Cf. A256816.

Sequence in context: A317475 A239751 A261782 * A048170 A067053 A271634

Adjacent sequences:  A256815 A256816 A256817 * A256819 A256820 A256821

KEYWORD

nonn

AUTHOR

R. H. Hardin, Apr 10 2015

STATUS

approved

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Last modified February 25 11:07 EST 2020. Contains 332231 sequences. (Running on oeis4.)