A248457 - OEIS

%I #8 Nov 08 2018 19:08:49

%S 96,380,1512,6040,24160,96736,387488,1552448,6220480,24926080,

%T 99883840,400260160,1603955712,6427525312,25757039296,103216337152,

%U 413619611968,1657501354048,6642119813120,26617026736320,106662654436544

%N Number of length n+2 0..4 arrays with no three consecutive terms having the sum of any two elements equal to twice the third.

%H R. H. Hardin, <a href="/A248457/b248457.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 3*a(n-1) + 5*a(n-2) + 2*a(n-3) - 16*a(n-4) - 28*a(n-5) - 8*a(n-6).

%F Empirical g.f.: 4*x*(24 + 23*x - 27*x^2 - 147*x^3 - 186*x^4 - 50*x^5) / ((1 - 2*x)*(1 - x - 7*x^2 - 16*x^3 - 16*x^4 - 4*x^5)). - _Colin Barker_, Nov 08 2018

%e Some solutions for n=6:

%e ..1....0....0....2....3....3....0....0....3....2....3....1....3....4....0....1

%e ..3....4....1....0....4....4....3....1....1....3....2....4....2....1....3....3

%e ..0....1....3....3....4....3....4....1....0....0....2....2....2....4....0....0

%e ..0....4....4....1....3....0....0....0....3....4....3....2....3....4....2....0

%e ..2....1....3....4....1....4....1....4....0....1....2....0....3....0....3....1

%e ..3....0....0....3....1....0....3....4....2....2....0....0....1....0....0....1

%e ..0....1....2....1....2....0....4....2....2....4....0....4....3....4....2....3

%e ..0....0....0....0....4....4....3....2....3....1....3....4....3....3....3....1

%Y Column 4 of A248461.

%K nonn

%O 1,1

%A _R. H. Hardin_, Oct 06 2014