OFFSET
0,2
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (6, 3, -2).
FORMULA
G.f.: 1+x*(8+2*x-2*x^2)/(1-6*x-3*x^2+2*x^3). - Colin Barker, Jan 04 2012
EXAMPLE
a(2) = 50 because if the middle row is not monochromatic, the top and bottom rows are unconstrained, contributing 2*4*4. if the middle row is monochromatic, the top and bottom rows can each take on only 3 values contributing 2*3*3.
CROSSREFS
KEYWORD
nonn
AUTHOR
Victor S. Miller, Sep 19 2007
EXTENSIONS
More terms from Colin Barker, Jan 03 2012
a(0)=1 prepended and g.f. adapted by Alois P. Heinz, Feb 19 2015
STATUS
approved