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A200880 Number of 0..2 arrays x(0..n+1) of n+2 elements without any interior element greater than both neighbors. 1
22, 51, 121, 292, 704, 1691, 4059, 9749, 23422, 56268, 135166, 324692, 779977, 1873673, 4500958, 10812237, 25973244, 62393157, 149881402, 360046432, 864906711, 2077686532, 4991036946, 11989513056, 28801314179, 69186771332 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Column 2 of A200886.
LINKS
FORMULA
Empirical: a(n) = 3*a(n-1) -3*a(n-2) +4*a(n-3) -a(n-4) +a(n-5).
Empirical g.f.: x*(22 - 15*x + 34*x^2 - 6*x^3 + 9*x^4) / (1 - 3*x + 3*x^2 - 4*x^3 + x^4 - x^5). - Colin Barker, Oct 16 2017
EXAMPLE
Some solutions for n=3
..2....0....2....0....2....1....2....2....2....1....1....1....0....2....2....1
..0....2....1....0....1....2....2....1....2....2....0....1....0....2....2....2
..1....2....0....2....1....2....0....2....0....2....1....1....1....1....2....2
..1....0....1....2....0....1....1....2....0....2....1....1....1....0....1....1
..0....1....2....0....1....1....1....1....1....2....1....0....1....1....2....2
CROSSREFS
Sequence in context: A015226 A092221 A191279 * A330409 A111576 A277979
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 23 2011
STATUS
approved

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Last modified July 14 05:06 EDT 2024. Contains 374291 sequences. (Running on oeis4.)