OFFSET
0,3
LINKS
S. Klavzar and Y. Rho, On the Wiener index of generalized Fibonacci cubes and Lucas cubes, preprint (2013).
FORMULA
There is an explicit formula for a(n) in terms of tribonacci numbers (A000073).
Empirical g.f.: x*(x^2+1)*(x^2+4*x+1) / ((x^3-x^2-x-1)^2*(x^3+x^2+3*x-1)^2). - Colin Barker, Sep 08 2013
PROG
(Magma) /* From Klavzar and Rho paper, Theorem 2.4: */ T:=[n le 3 select Floor(n/3) else Self(n-1)+Self(n-2)+Self(n-3): n in [1..40]]; /* being T=A000073 */ [((268+67*n)*T[n+4]^2-(118+4*n)*T[n+4]*T[n+5]-(50-14*n)*T[n+4]*T[n+6] -(66+7*n)*T[n+5]^2+(90+16*n)*T[n+5]*T[n+6]-(18+6*n)*T[n+6]^2)/484: n in [0..#T-6]]; // Bruno Berselli, Sep 06 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Sep 06 2013
EXTENSIONS
More terms from Bruno Berselli, Sep 06 2013
STATUS
approved