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A256821 Number of length n+6 0..1 arrays with at most two downsteps in every n consecutive neighbor pairs. 1
128, 256, 512, 1024, 1888, 3204, 5088, 7677, 11120, 15579, 21230, 28264, 36888, 47326, 59820, 74631, 92040, 112349, 135882, 162986, 194032, 229416, 269560, 314913, 365952, 423183, 487142, 558396, 637544, 725218, 822084, 928843, 1046232 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Row 6 of A256816.

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 + (111/8)*n^3 - (701/24)*n^2 + (11767/60)*n - 253 for n>4.

Empirical g.f.: x*(128 - 512*x + 896*x^2 - 768*x^3 + 224*x^4 + 68*x^5 - 24*x^6 - 7*x^7 - 14*x^8 + 10*x^9) / (1 - x)^6. - Colin Barker, Jan 21 2018

EXAMPLE

Some solutions for n=4:

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

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

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

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

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

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

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

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

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

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

CROSSREFS

Cf. A256816.

Sequence in context: A110290 A045028 A255997 * A172421 A235059 A045053

Adjacent sequences:  A256818 A256819 A256820 * A256822 A256823 A256824

KEYWORD

nonn

AUTHOR

R. H. Hardin, Apr 10 2015

STATUS

approved

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Last modified October 27 02:00 EDT 2021. Contains 348270 sequences. (Running on oeis4.)