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A256817
Number of length n+2 0..1 arrays with at most two downsteps in every n consecutive neighbor pairs.
1
8, 16, 32, 64, 124, 229, 402, 673, 1080, 1670, 2500, 3638, 5164, 7171, 9766, 13071, 17224, 22380, 28712, 36412, 45692, 56785, 69946, 85453, 103608, 124738, 149196, 177362, 209644, 246479, 288334, 335707, 389128, 449160, 516400, 591480, 675068
OFFSET
1,1
COMMENTS
Row 2 of A256816.
LINKS
FORMULA
Empirical: a(n) = (1/120)*n^5 + (1/24)*n^4 + (3/8)*n^3 - (1/24)*n^2 + (277/60)*n + 3.
Empirical g.f.: x*(8 - 32*x + 56*x^2 - 48*x^3 + 20*x^4 - 3*x^5) / (1 - x)^6. - Colin Barker, Jan 21 2018
EXAMPLE
Some solutions for n=4:
..0....0....1....0....0....0....1....1....0....0....1....0....0....1....0....0
..0....0....1....0....0....1....0....1....1....0....0....1....1....1....0....1
..0....1....1....1....1....0....0....1....0....0....0....0....1....0....0....0
..0....0....1....0....0....0....1....0....1....1....0....1....0....0....0....0
..0....1....0....0....0....1....1....0....1....0....1....0....1....0....0....1
..1....1....0....1....0....1....1....0....0....1....1....1....1....0....0....0
CROSSREFS
Cf. A256816.
Sequence in context: A054743 A192135 A345053 * A281016 A048169 A089882
KEYWORD
nonn
AUTHOR
R. H. Hardin, Apr 10 2015
STATUS
approved