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A255111
Number of length n+4 0..2 arrays with at most one downstep in every n consecutive neighbor pairs.
1
243, 622, 1137, 1905, 2951, 4338, 6141, 8448, 11361, 14997, 19489, 24987, 31659, 39692, 49293, 60690, 74133, 89895, 108273, 129589, 154191, 182454, 214781, 251604, 293385, 340617, 393825, 453567, 520435, 595056, 678093, 770246, 872253, 984891
OFFSET
1,1
COMMENTS
Row 4 of A255107.
LINKS
FORMULA
Empirical: a(n) = (1/120)*n^5 + (7/24)*n^4 + (85/24)*n^3 + (1505/24)*n^2 + (2809/20)*n + 30 for n>2.
Empirical g.f.: x*(243 - 836*x + 1050*x^2 - 447*x^3 - 219*x^4 + 339*x^5 - 156*x^6 + 27*x^7) / (1 - x)^6. - Colin Barker, Jan 24 2018
EXAMPLE
Some solutions for n=4:
1 1 0 0 2 2 1 2 0 0 2 2 1 2 0 0
1 1 0 2 0 0 2 0 0 2 2 2 2 0 1 2
1 2 0 1 1 0 2 2 2 1 2 2 0 0 1 1
0 2 1 1 1 0 1 2 2 1 2 2 0 0 2 2
0 2 2 1 1 1 2 2 2 1 1 2 2 0 2 2
0 2 2 2 2 2 2 2 2 2 1 1 2 1 0 2
1 2 0 0 1 2 2 0 2 2 2 1 2 2 2 2
0 2 0 0 1 2 0 2 0 2 2 2 1 1 2 0
CROSSREFS
Cf. A255107.
Sequence in context: A232924 A067838 A340757 * A353320 A331613 A255626
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 14 2015
STATUS
approved