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 A133646 a(n)=5*a(n-1)+30*a(n-2) for n>=3, a(0)=1, a(1)=5, a(2)=50 . 2

%I

%S 1,5,50,400,3500,29500,252500,2147500,18312500,155987500,1329312500,

%T 11326187500,96510312500,822337187500,7006995312500,59705092187500,

%U 508735320312500,4334829367187500,36936206445312500,314725913242187500

%N a(n)=5*a(n-1)+30*a(n-2) for n>=3, a(0)=1, a(1)=5, a(2)=50 .

%F G.f.: (1-5*x^2)/(1-5*x-30*x^2) . a(n) = Sum_{k, 0<=k<=n}A122950(n,k)*5^k .

%F a(n)=(5/2)*[(5/2)-(1/2)*sqrt(145)]^(n-1)-(15/58)*[(5/2)-(1/2)*sqrt(145)]^(n-1)*sqrt(145)+(15/58)*sqrt(145) *[(5/2)+(1/2)*sqrt(145)]^(n-1)+(5/2)*[(5/2)+(1/2)*sqrt(145)]^(n-1)+(1/6)*[C(2*n,n) mod 2], with n>=0

%K easy,nonn

%O 0,2

%A _Philippe DelĂ©ham_, Dec 31 2007

%E Corrected formula. - _Paolo P. Lava_, Nov 24 2008

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Last modified March 29 17:51 EDT 2023. Contains 361599 sequences. (Running on oeis4.)