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A070876
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Binary expansion is 1xx100...0 where xx = 00 or 11.
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3
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9, 15, 18, 30, 36, 60, 72, 120, 144, 240, 288, 480, 576, 960, 1152, 1920, 2304, 3840, 4608, 7680, 9216, 15360, 18432, 30720, 36864, 61440, 73728, 122880, 147456, 245760, 294912, 491520, 589824, 983040, 1179648, 1966080, 2359296, 3932160
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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LINKS
| Index entries for sequences related to linear recurrences with constant coefficients, signature (0,2).
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FORMULA
| Contribution by Bruno Berselli, Mar 02 2011: (Start)
G.f.: 3*(3+5*x)/(1-2*x^2).
a(n) = 3*(4-(-1)^n)*2^((2*n+(-1)^n-1)/4). Therefore: a(n) = 9*2^(n/2) for n even, otherwise a(n) = 15*2^((n-1)/2).
a(n) = 2*a(n-2) for n>1. (End)
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MATHEMATICA
| a = {}; Do[a = Append[a, FromDigits[ Join[{1, 0, 0, 1}, Table[0, {n}]], 2]]; a = Append[a, FromDigits[ Join[{1, 1, 1, 1}, Table[0, {n}]], 2]], {n, 0, 20}]; a
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PROG
| (MAGMA) [n le 2 select 6*n+3 else 2*Self(n-2): n in [1..38]]; // Bruno Berselli, mar 02 2011
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CROSSREFS
| Cf. A070875.
Sequence in context: A093642 A177733 A118236 * A161163 A058211 A038599
Adjacent sequences: A070873 A070874 A070875 * A070877 A070878 A070879
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), May 19 2002
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EXTENSIONS
| More terms from Robert G. Wilson v (rgwv(AT)rgwv.com), May 20 2002
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