OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 16*a(n-1) - 48*a(n-2) for n>3.
Conjectures from Colin Barker, Oct 11 2018: (Start)
G.f.: x*(3 - 38*x + 88*x^2) / ((1 - 4*x)*(1 - 12*x)).
a(n) = 2^(2*n-3) * (4*3^n+9) / 9 for n>1.
(End)
EXAMPLE
Some solutions for n=5:
..0..1..2..5..3....0..1..2..4..3....0..1..5..4..2....0..1..2..1..0
..0..4..2..1..2....5..1..5..4..2....2..4..3..1..2....2..1..5..4..0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 06 2013
STATUS
approved