OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 4*a(n-1) + 20*a(n-2) - 80*a(n-3).
Conjectures from Colin Barker, Oct 13 2018: (Start)
G.f.: 4*x*(26 + 5*x - 500*x^2) / ((1 - 4*x)*(1 - 20*x^2)).
a(n) = 4^(2+n) + 2^(-1+n)*5^((-1+n)/2) * (20-20*(-1)^n+9*sqrt(5)+9*(-1)^n*sqrt(5)).
(End)
EXAMPLE
Some solutions for n=5:
3 3 0 3 2 0 0 1 0 2 1 1 0 3 1 4 2 2 1 1
3 0 3 3 2 3 0 4 3 2 4 1 2 2 3 3 1 4 4 1
4 4 4 1 3 1 3 4 4 0 4 4 4 1 1 4 4 4 4 4
1 4 4 4 2 3 2 0 2 1 1 4 1 1 0 0 0 3 3 0
3 3 3 0 4 2 0 1 4 0 1 1 4 1 3 0 0 0 3 3
3 0 4 4 3 4 3 1 3 2 0 3 0 0 4 4 1 4 0 3
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 21 2013
STATUS
approved