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A200881 Number of 0..3 arrays x(0..n+1) of n+2 elements without any interior element greater than both neighbors. 1
50, 144, 422, 1268, 3823, 11472, 34350, 102896, 308419, 924532, 2771101, 8305373, 24892609, 74608516, 223618304, 670231838, 2008825312, 6020872062, 18045827096, 54087163859, 162110668160, 485879938474, 1456284886944, 4364793695063 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 3 of A200886.

LINKS

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

FORMULA

Empirical: a(n) = 4*a(n-1) -6*a(n-2) +10*a(n-3) -5*a(n-4) +6*a(n-5) -a(n-6) +a(n-7).

Empirical g.f.: x*(50 - 56*x + 146*x^2 - 56*x^3 + 93*x^4 - 12*x^5 + 16*x^6) / (1 - 4*x + 6*x^2 - 10*x^3 + 5*x^4 - 6*x^5 + x^6 - x^7). - Colin Barker, Oct 16 2017

EXAMPLE

Some solutions for n=3

..2....2....2....3....0....3....1....1....3....3....1....3....0....1....3....1

..0....2....1....2....0....3....1....2....2....3....0....3....1....1....1....2

..2....1....0....0....2....3....0....2....1....1....1....1....3....0....3....3

..2....2....0....1....3....3....2....0....2....1....2....0....3....0....3....3

..0....2....2....2....3....2....3....3....3....2....3....3....1....3....3....3

CROSSREFS

Sequence in context: A043474 A044301 A044682 * A235942 A093300 A283392

Adjacent sequences:  A200878 A200879 A200880 * A200882 A200883 A200884

KEYWORD

nonn

AUTHOR

R. H. Hardin, Nov 23 2011

STATUS

approved

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Last modified March 24 00:12 EDT 2019. Contains 321444 sequences. (Running on oeis4.)