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A218189
Hilltop maps: number of n X 1 binary arrays indicating the locations of corresponding elements not exceeded by any horizontal or vertical neighbor in a random 0..3 n X 1 array.
5
1, 3, 7, 15, 29, 57, 113, 225, 449, 895, 1783, 3551, 7073, 14089, 28065, 55905, 111361, 221827, 441871, 880191, 1753309, 3492529, 6956993, 13858081, 27604801, 54987775, 109533679, 218187167, 434621025, 865749521, 1724542049, 3435226017
OFFSET
1,2
COMMENTS
Column 1 of A218196.
LINKS
FORMULA
Empirical: a(n) = a(n-1) + a(n-2) + a(n-3) + a(n-4) + a(n-5) + a(n-6) + a(n-7).
Empirical g.f.: x*(1 + x)^2*(1 + x^2)^2 / (1 - x - x^2 - x^3 - x^4 - x^5 - x^6 - x^7). - Colin Barker, Feb 19 2018
EXAMPLE
All solutions for n=3:
..1....1....1....0....0....0....1
..0....1....0....1....0....1....1
..1....0....0....1....1....0....1
CROSSREFS
Sequence in context: A321309 A373090 A023608 * A132780 A018087 A171625
KEYWORD
nonn
AUTHOR
R. H. Hardin, Oct 23 2012
STATUS
approved