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A123270
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a(0)=1, a(1)=1, a(n) = 5*a(n-1) + 4*a(n-2).
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6
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1, 1, 9, 49, 281, 1601, 9129, 52049, 296761, 1692001, 9647049, 55003249, 313604441, 1788035201, 10194593769, 58125109649, 331403923321, 1889520055201, 10773215969289, 61424160067249, 350213664213401, 1996764961336001
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OFFSET
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0,3
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COMMENTS
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First differences give {0, 8, 40, 232, 1320, 7528, 42920, ...} = 8*A015537(n) = 8 * {0, 1, 5, 29, 165, 941, 5365, ...}. - Alexander Adamchuk, Nov 03 2006
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LINKS
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FORMULA
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a(n) = Sum_{k=0..n} 4^(n-k)*A122542(n,k).
G.f.: (1-4*x)/(1-5*x-4*x^2).
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MATHEMATICA
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LinearRecurrence[{5, 4}, {1, 1}, 30] (* Harvey P. Dale, Jul 25 2011 *)
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PROG
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(Haskell)
a123270 n = a123270_list !! n
a123270_list = 1 : 1 : zipWith (-) (map (* 5) $
zipWith (+) (tail a123270_list) a123270_list) a123270_list
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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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