OFFSET
2,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 2..52
FORMULA
Empirical: a(n) = 12*a(n-1) - 63*a(n-2) + 190*a(n-3) - 363*a(n-4) + 456*a(n-5) - 377*a(n-6) + 198*a(n-7) - 60*a(n-8) + 8*a(n-9) for n >= 11.
Empirical g.f.: 2*x^2*(4 + 6*x - 31*x^2 + 50*x^3 - 62*x^4 + 52*x^5 - 7*x^6 - 12*x^7 + 4*x^8) / ((1 - x)^6*(1 - 2*x)^3). - Colin Barker, Mar 25 2018
EXAMPLE
Some solutions for n=4:
1 1 2 1 2 2 1 1 2 1 1 2 1 2 2 1 1 2 1 1 2 1 1 2 1 2 2
1 1 1 1 4 4 1 4 4 3 2 2 2 2 2 3 3 2 3 1 2 1 1 1 1 1 4
3 4 4 4 4 4 4 4 4 3 2 4 4 4 2 3 3 2 3 3 4 3 1 1 1 1 4
3 3 4 3 3 4 3 3 4 3 4 4 3 4 4 3 4 4 3 3 4 3 4 4 3 4 4
------
1 2 2 1 1 2 1 4 2 1 2 2 1 2 2 1 2 2 1 2 2 1 1 2 1 2 2
1 2 2 1 2 2 1 4 4 1 3 2 1 1 1 3 3 3 1 2 2 3 4 2 1 1 2
2 2 4 1 2 2 1 4 4 3 3 3 3 3 3 3 3 4 3 3 2 3 4 4 3 1 4
3 3 4 3 4 4 3 3 4 3 4 4 3 3 4 3 4 4 3 3 4 3 3 4 3 1 4
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Aug 24 2009
STATUS
approved