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A087404
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a(n)=4a(n-1)+5a(n-2).
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2
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2, 4, 26, 124, 626, 3124, 15626, 78124, 390626, 1953124, 9765626, 48828124, 244140626, 1220703124, 6103515626, 30517578124, 152587890626, 762939453124, 3814697265626, 19073486328124, 95367431640626, 476837158203124
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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FORMULA
| G.f.: (2-4x)/(1-4x-5x^2). a(n)=5^n+(-1)^n
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MATHEMATICA
| CoefficientList[Series[(2 - 4x)/(1 - 4x - 5x^2), {x, 0, 25}], x]
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PROG
| (Other) sage: [lucas_number2(n, 4, -5) for n in xrange(0, 22)]# [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), May 14 2009]
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CROSSREFS
| Sequence in context: A155120 A144691 A085700 * A009237 A019019 A032328
Adjacent sequences: A087401 A087402 A087403 * A087405 A087406 A087407
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KEYWORD
| easy,nonn
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AUTHOR
| Mario Catalani (mario.catalani(AT)unito.it), Sep 01 2003
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