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Search: id:A155988
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| 1, 27, 405, 5103, 59049, 649539, 6908733, 71744535, 731794257, 7360989291, 73222472421, 721764371007, 7060738412025, 68630377364883, 663426981193869, 6382625094934119, 61149666232110753, 583701359488329915
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OFFSET
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0,2
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COMMENT
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Sum(n>=0,1/a(n))=(3/2)log(2)
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LINKS
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David H. Bailey, A Compendium of BBP-Type Formulas for Mathematical Constants, page 14. [From Jaume Oliver Lafont (joliverlafont(AT)gmail.com), Sep 25 2009]
X. Gourdon and P. Sebah, Collection of formulae for log 2
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FORMULA
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G.f.: (1+9x)/(1-9x)^2
Linear recurrence: a(0)=1, a(1)=27, a(n)=18a(n-1)-81a(n-2) for n>=2
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PROGRAM
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(PARI) a(n)=(2*n+1)*9^n;
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CROSSREFS
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a(n)=A005408(n)*A001019(n). Cf. A096949, A096950, A058962 (2n+1)4^n.
Cf. A154920, A164985, A165132. [From Jaume Oliver Lafont (joliverlafont(AT)gmail.com), Sep 25 2009]
Sequence in context: A125462 A036222 A022655 this_sequence A096950 A125484 A022751
Adjacent sequences: A155985 A155986 A155987 this_sequence A155989 A155990 A155991
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KEYWORD
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nonn
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AUTHOR
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Jaume Oliver Lafont (joliverlafont(AT)gmail.com), Feb 01 2009
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