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%I #6 Mar 30 2012 18:39:03
%S 9,9,9,15,23,51,93,225,429,1059,2039,5055,9753,24201,46713,115935,
%T 223799,555459,1072269,2661345,5137533,12751251,24615383,61094895,
%U 117939369,292723209,565081449,1402521135,2707467863,6719882451
%N 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).
%C All terms are integers.
%F lim n -> infinity a(n+1)/a(n) = (1/6) * ( 7 + sqrt(21) ) = 1.93042928249263...
%F G.f.: x(15x^5+23x^4-39x^3-45x^2+9x+9)/(-x^6+6x^4-6x^2+1).
%Y Cf. A072881, A072557, A072560, A072561.
%K nonn
%O 1,1
%A _Benoit Cloitre_, Aug 06 2002
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