A072563 9*w(n) where : w(1)=w(2)=w(3)=1 w(n)=(w(n-1)*w(n-2)+(w(n-1)+w(n-2))/3) / w(n-3).

9, 9, 9, 15, 23, 51, 93, 225, 429, 1059, 2039, 5055, 9753, 24201, 46713, 115935, 223799, 555459, 1072269, 2661345, 5137533, 12751251, 24615383, 61094895, 117939369, 292723209, 565081449, 1402521135, 2707467863, 6719882451

Offset: 1

Author

Benoit Cloitre, Aug 06 2002

Keywords

• nonn

Comments

All terms are integers.

Crossrefs

Cf. A072881, A072557, A072560, A072561.

Formula

lim n -> infinity a(n+1)/a(n) = (1/6) * ( 7 + sqrt(21) ) = 1.93042928249263...

G.f.: x(15x^5+23x^4-39x^3-45x^2+9x+9)/(-x^6+6x^4-6x^2+1).