

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
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OFFSET

1,1


COMMENTS

Column 2 of A200886.


LINKS

R. H. Hardin, Table of n, a(n) for n = 1..210


FORMULA

Empirical: a(n) = 3*a(n1) 3*a(n2) +4*a(n3) a(n4) +a(n5).
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
Adjacent sequences: A200877 A200878 A200879 * A200881 A200882 A200883


KEYWORD

nonn


AUTHOR

R. H. Hardin, Nov 23 2011


STATUS

approved



