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A084329
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a(0)=0, a(1)=1, a(n)=20a(n-1)-20a(n-2).
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1
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0, 1, 20, 380, 7200, 136400, 2584000, 48952000, 927360000, 17568160000, 332816000000, 6304956800000, 119442816000000, 2262757184000000, 42866287360000000, 812070603520000000, 15384086323200000000
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OFFSET
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0,3
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LINKS
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FORMULA
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a(n)=(1/8)*sum(k=0, n, binomial(n, k)*F(6*k)) where F(k) denotes the k-th Fibonacci number.
G.f.: x/(1-20x+20x^2).
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MATHEMATICA
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Union[Flatten[NestList[{#[[2]], 20(#[[2]]-#[[1]])}&, {0, 1}, 20]]] (*Harvey P. Dale,Feb 24 2011 *)
LinearRecurrence[{20, -20}, {0, 1}, 20] (*Harvey P. Dale,Nov 29 2019 *)
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PROG
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(PARI) a(n)=(1/8)*sum(k=0, n, binomial(n, k)*fibonacci(6*k))
(PARI) a(n)=imag((6+8*quadgen(5))^n)/8
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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