OFFSET
3,1
COMMENTS
First differences of (a(3k), a(3k + 1)), (a(3k + 1), a(3k + 2)), (a(3k + 2), a(3k + 3)) seem to be 4 * 3^(k - 1). - David A. Corneth, Apr 15 2015
FORMULA
Conjectured g.f.: x^3*(3 + 4*x+ 4*x^2 - 5*x^3)/(1 - x - 3*x^3 + 3*x^4). - Alexander R. Povolotsky, Apr 15 2015
Conjectured formula: a(n) = 6*(3^(floor(n / 3))/3 - 1) + 3 + 4 * (n mod 3) * 3^(floor(n / 3))/3. - David A. Corneth, Apr 15 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Sep 30 2008
STATUS
approved