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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

%I

%S 22,51,121,292,704,1691,4059,9749,23422,56268,135166,324692,779977,

%T 1873673,4500958,10812237,25973244,62393157,149881402,360046432,

%U 864906711,2077686532,4991036946,11989513056,28801314179,69186771332

%N Number of 0..2 arrays x(0..n+1) of n+2 elements without any interior element greater than both neighbors.

%C Column 2 of A200886.

%H R. H. Hardin, <a href="/A200880/b200880.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 3*a(n-1) -3*a(n-2) +4*a(n-3) -a(n-4) +a(n-5).

%F 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

%e Some solutions for n=3

%e ..2....0....2....0....2....1....2....2....2....1....1....1....0....2....2....1

%e ..0....2....1....0....1....2....2....1....2....2....0....1....0....2....2....2

%e ..1....2....0....2....1....2....0....2....0....2....1....1....1....1....2....2

%e ..1....0....1....2....0....1....1....2....0....2....1....1....1....0....1....1

%e ..0....1....2....0....1....1....1....1....1....2....1....0....1....1....2....2

%K nonn

%O 1,1

%A _R. H. Hardin_, Nov 23 2011

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Last modified March 19 04:34 EDT 2019. Contains 321311 sequences. (Running on oeis4.)