A211532 - OEIS

%I #7 Jul 19 2018 05:18:43

%S 8,22,46,100,204,422,856,1744,3526,7136,14388,29006,58352,117336,

%T 235638,473000,948684,1902030,3811400,7635312,15290470,30614320,

%U 61281860,122652366,245446592,491127784,982632022,1965883288,3932762268

%N Number of -1..1 arrays x(i) of n+1 elements i=1..n+1 with set{t,u,v in 0,1}((x[i+t]+x[j+u]+x[k+v])*(-1)^(t+u+v)) having two, four, five, six or seven distinct values for every i,j,k<=n.

%H R. H. Hardin, <a href="/A211532/b211532.txt">Table of n, a(n) for n = 1..58</a>

%F Empirical: a(n) = 3*a(n-1) + 2*a(n-2) - 11*a(n-3) + a(n-4) + 12*a(n-5) - 2*a(n-6) - 4*a(n-7).

%F Empirical g.f.: 2*x*(4 - x - 18*x^2 + 3*x^3 + 23*x^4 - x^5 - 6*x^6) / ((1 - x)*(1 + x)*(1 - 2*x)*(1 - x - x^2)*(1 - 2*x^2)). - _Colin Barker_, Jul 19 2018

%e Some solutions for n=5:

%e .-1....1....1....0...-1....0....1...-1....0....1...-1....0...-1....0...-1....1

%e ..0...-1...-1....1...-1....1....1....0...-1....1....0....1...-1....1...-1....1

%e .-1....1....1...-1...-1....1....0...-1...-1...-1...-1....1....0....0...-1....0

%e ..0...-1...-1....1...-1....0....1....1...-1....1....1...-1...-1....1...-1....1

%e .-1....1....1....1....0....1....1...-1....0...-1...-1....1....0....1...-1...-1

%e ..0...-1....1....0...-1....1....0...-1...-1....1....0....0...-1....0....1....1

%K nonn

%O 1,1

%A _R. H. Hardin_, Apr 14 2012