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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
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: A260200 A178100 A357569 * A304673 A039458 A291672
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 13 2015
STATUS
approved

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Last modified April 13 02:05 EDT 2024. Contains 371639 sequences. (Running on oeis4.)