OFFSET
0,2
LINKS
Index entries for linear recurrences with constant coefficients, signature (0,0,2,0,0,-1).
FORMULA
a(n) = #{0<=k<=n: 3 divides k(n-k)}.
G.f.: ( 1+2*x+2*x^2 ) / ( (x-1)^2*(1+x+x^2)^2 ). - R. J. Mathar, Feb 14 2015
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Sep 14 2003
STATUS
approved