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Search: id:A053524
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| 0, 1, 4, 28, 160, 976, 5824, 35008, 209920, 1259776, 7558144, 45349888, 272097280, 1632587776, 9795518464, 58773127168, 352638730240, 2115832446976, 12694994550784, 76169967566848, 457019804876800, 2742118830309376, 16452712979759104
(list; graph; listen)
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OFFSET
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0,3
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REFERENCES
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R. P. Stanley, Enumerative Combinatorics, Cambridge, Vol. 2, 1999; see Problem 5.1(b).
A. H. Beiler, Recreations in the Theory of Numbers, Dover, NY, 1964, pp. 194-196.
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FORMULA
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E.g.f.: (e^{6x}-e^{-2x))/8.
a(n) = 2^n/8(3^n-(-1)^n). a(n)=4a(n-1)+12a(n-2); a(0)=0, a(1)=1.
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CROSSREFS
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Cf. A015518.
Sequence in context: A123520 A012847 A128721 this_sequence A125687 A026298 A129587
Adjacent sequences: A053521 A053522 A053523 this_sequence A053525 A053526 A053527
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KEYWORD
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nonn,easy
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AUTHOR
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njas, Barry E. Williams, Jan 15 2000
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