OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = a(n-1) + 2*a(n-6) - 2*a(n-7) - a(n-12) + a(n-13).
Empirical for n mod 6 = 0: a(n) = (4/9)*n^2 + (1/3)*n
Empirical for n mod 6 = 1: a(n) = (4/9)*n^2 + (11/18)*n + (17/18)
Empirical for n mod 6 = 2: a(n) = (4/9)*n^2 + (13/18)*n + (7/9)
Empirical for n mod 6 = 3: a(n) = (4/9)*n^2 + 1*n
Empirical for n mod 6 = 4: a(n) = (4/9)*n^2 + (4/9)*n + (1/9)
Empirical for n mod 6 = 5: a(n) = (4/9)*n^2 + (8/9)*n + (4/9).
Empirical g.f.: x*(2 + 2*x + 3*x^2 + 2*x^3 + 7*x^4 + 2*x^5 + 5*x^6 + 4*x^7 + 4*x^8 + x^10) / ((1 - x)^3*(1 + x)^2*(1 - x + x^2)^2*(1 + x + x^2)^2). - Colin Barker, Dec 20 2018
EXAMPLE
All solutions for n=4:
..2....4....4....3....3....2....3....2....4
..1....2....4....1....3....2....5....4....5
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Apr 15 2015
STATUS
approved