OFFSET
1,2
COMMENTS
Column 2 of A180771
LINKS
R. H. Hardin, Table of n, a(n) for n=1..99
FORMULA
Empirical: a(n) = 3*a(n-1) + a(n-2) - 2*a(n-4).
Empirical G.f.: x*(1-x)*(1+x+2*x^2)/(1-3*x-x^2+2*x^4). [Colin Barker, Feb 22 2012]
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin Sep 20 2010
STATUS
approved