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A255988 Number of length n+4 0..1 arrays with at most one downstep in every 4 consecutive neighbor pairs. 1
26, 45, 80, 144, 256, 451, 796, 1413, 2510, 4448, 7872, 13943, 24718, 43817, 77636, 137540, 243712, 431899, 765360, 1356169, 2403034, 4258172, 7545592, 13370799, 23692770, 41983189, 74394040, 131826104, 233594880, 413927683, 733476228 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 4 of A255992.

LINKS

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

FORMULA

Empirical: a(n) = 2*a(n-1) -a(n-2) +3*a(n-4) -2*a(n-5).

Empirical g.f.: x*(26 - 7*x + 16*x^2 + 29*x^3 - 30*x^4) / (1 - 2*x + x^2 - 3*x^4 + 2*x^5). - Colin Barker, Jan 24 2018

EXAMPLE

Some solutions for n=4:

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

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

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

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

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

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

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

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

CROSSREFS

Cf. A255992.

Sequence in context: A217775 A260200 A178100 * A304673 A039458 A291672

Adjacent sequences:  A255985 A255986 A255987 * A255989 A255990 A255991

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 13 2015

STATUS

approved

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Last modified January 18 00:11 EST 2021. Contains 340249 sequences. (Running on oeis4.)