OFFSET
1,2
COMMENTS
Column 1 of A232589.
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = 2*a(n-1) - a(n-2) + a(n-3) = 2*A005314(n-1).
Empirical: G.f.: -2*x^2 / ( -1+2*x-x^2+x^3 ). - R. J. Mathar, Nov 23 2014
Theorem: a(n) = Sum_{j=1..floor((n-2)/3)} 2* Hypergeometric2F1([2+3*j-n,-(2j+1)], [1], 1). - Richard Turk, Oct 22 2019
EXAMPLE
Some solutions for n=7:
2 1 0 1 2 1 0 1 0 1 0 1 0 1 2 1 0 1 2 1
0 1 2 1 0 1 2 0 2 1 2 0 2 1 0 2 2 0 0 1
2 0 0 1 2 0 1 2 0 2 1 2 0 1 1 0 1 2 2 0
1 2 2 1 1 2 1 0 1 0 0 1 2 0 1 2 0 1 1 2
1 0 0 1 0 1 2 1 2 1 2 0 1 2 1 0 2 1 1 0
1 2 2 0 2 1 0 2 0 1 1 2 0 1 1 2 0 2 2 1
1 0 1 2 0 2 1 0 2 0 1 0 2 0 1 0 1 0 0 2
1 2 1 0 1 0 1 2 1 2 1 2 1 2 1 2 1 2 1 0
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 26 2013
STATUS
approved