login
A245864
Number of length n+2 0..2 arrays with some pair in every consecutive three terms totalling exactly 2.
1
19, 45, 103, 239, 553, 1281, 2967, 6873, 15921, 36881, 85435, 197911, 458463, 1062035, 2460217, 5699123, 13202089, 30582803, 70845443, 164114349, 380172929, 880675315, 2040095313, 4725906149, 10947620333, 25360298571, 58747446847
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = 2*a(n-1) + a(n-2) - a(n-4) - a(n-5).
Empirical g.f.: x*(19 + 7*x - 6*x^2 - 12*x^3 - 9*x^4) / ((1 - x)*(1 - x - 2*x^2 - 2*x^3 - x^4)). - Colin Barker, Nov 03 2018
EXAMPLE
Some solutions for n=10:
..1....2....1....2....0....1....0....1....0....0....2....0....0....2....0....0
..1....1....1....2....0....1....2....1....2....1....2....1....0....1....1....1
..1....1....1....0....2....1....1....1....0....1....0....2....2....0....1....1
..1....0....0....2....1....1....1....1....2....2....2....0....0....2....2....0
..1....2....2....0....1....1....1....2....2....0....1....2....2....2....0....1
..0....2....0....1....2....2....0....1....0....1....1....0....1....0....2....2
..2....0....1....1....0....1....2....0....2....1....0....2....1....2....2....0
..2....1....1....1....2....0....0....2....2....1....1....1....1....2....0....1
..0....2....2....1....0....1....0....1....0....1....1....1....0....0....0....1
..2....1....1....0....1....2....2....1....1....1....1....0....1....0....2....0
..2....0....0....1....1....1....0....2....2....2....1....2....1....2....2....1
..0....1....1....1....1....0....2....1....0....1....1....0....2....0....0....2
CROSSREFS
Column 2 of A245869.
Sequence in context: A140680 A183632 A359558 * A183624 A115249 A325451
KEYWORD
nonn
AUTHOR
R. H. Hardin, Aug 04 2014
STATUS
approved