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A135440
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a(n)=a(n-1)+2a(n-2).
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2
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-1, 4, 2, 10, 14, 34, 62, 130, 254, 514, 1022, 2050, 4094, 8194, 16382, 32770, 65534, 131074, 262142, 524290, 1048574, 2097154, 4194302, 8388610, 16777214, 33554434, 67108862, 134217730, 268435454, 536870914, 1073741822, 2147483650, 4294967294, 8589934594, 17179869182, 34359738370
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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FORMULA
| O.g.f.: -1/(2*x-1)-2/(1+x). a(n) = 2^n-2*(-1)^n. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Feb 19 2008
a(n) = 2*A014551(n-1), n>0. - Paul Curtz, Jun 01 2011
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MATHEMATICA
| f[n_]:=2/(n+1); x=4; Table[x=f[x]; Numerator[x], {n, 0, 5!}] [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Mar 12 2010]
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CROSSREFS
| Sequence in context: A121794 A075086 A128781 * A188128 A091484 A163544
Adjacent sequences: A135437 A135438 A135439 * A135441 A135442 A135443
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KEYWORD
| sign,easy
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AUTHOR
| Paul Curtz (bpcrtz(AT)free.fr), Feb 18 2008
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EXTENSIONS
| More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Feb 19 2008
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