A249701 - OEIS

%I #9 Nov 09 2018 14:21:15

%S 39,69,125,221,377,659,1177,2119,3805,6857,12437,22681,41475,76011,

%T 139645,257161,474439,876539,1621387,3002407,5564769,10321599,

%U 19156321,35571383,66081147,122803551,228283091,424467169,789412673,1468380739

%N Number of length n+3 0..2 arrays with every four consecutive terms having the maximum of some two terms equal to the minimum of the remaining two terms.

%H R. H. Hardin, <a href="/A249701/b249701.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 3*a(n-1) - 3*a(n-2) + 2*a(n-3) + 2*a(n-4) - 5*a(n-5) + a(n-6) -a(n-7) - 2*a(n-8) + 2*a(n-10).

%F Empirical g.f.: x*(39 - 48*x + 35*x^2 - 25*x^3 - 127*x^4 - 2*x^5 - 55*x^6 - 36*x^7 + 34*x^8 + 54*x^9) / ((1 + x)*(1 - 2*x + 2*x^2 - 2*x^3)*(1 - 2*x + x^2 - x^3 - x^4 + x^6)). - _Colin Barker_, Nov 09 2018

%e Some solutions for n=6:

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

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

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

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

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

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

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

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

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

%Y Column 2 of A249707.

%K nonn

%O 1,1

%A _R. H. Hardin_, Nov 04 2014