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Search: id:A117189
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| 1, 2, 5, 14, 40, 114, 324, 920, 2612, 7416, 21056, 59784, 169744, 481952, 1368400, 3885280, 11031424, 31321376, 88930368, 252498816, 716916544, 2035531648, 5779458048, 16409538688, 46591385856, 132286304768, 375598753024
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OFFSET
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1,2
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COMMENT
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a(n)/a(n-1) tends to 2.83928675...(the tribonacci constant 1.83928675...+ 1)
Partial sums are in A073357. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 02 2008
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FORMULA
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Binomial transform of A000073 starting with A000073(2): (1, 1, 2, 4, 7, 13...).
a(1)=1, a(2)=2, a(3)=5, a(n)=4a(n-1)-4a(n-2)+2a(n-3) - T. D. Noe (noe(AT)sspectra.com), Nov 07 2006
O.g.f.: -(x-1)^2/(-1+4*x-4*x^2+2*x^3). - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 02 2008
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EXAMPLE
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a(4) = 14 = 1*1 + 3*1 + 3*2 + 1*4
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CROSSREFS
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Cf. A000073.
Sequence in context: A111109 A081908 A059505 this_sequence A052963 A036908 A126220
Adjacent sequences: A117186 A117187 A117188 this_sequence A117190 A117191 A117192
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KEYWORD
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nonn
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AUTHOR
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Gary W. Adamson (qntmpkt(AT)yahoo.com), Mar 01 2006
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EXTENSIONS
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Corrected and extended by T. D. Noe (noe(AT)sspectra.com), Nov 07 2006
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