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Search: id:A000989
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| A000989 |
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3^a(n) divides C(2n,n). |
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+0
3
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| 0, 0, 1, 0, 0, 2, 1, 1, 2, 0, 0, 1, 0, 0, 3, 2, 2, 3, 1, 1, 2, 1, 1, 3, 2, 2, 3, 0, 0, 1, 0, 0, 2, 1, 1, 2, 0, 0, 1, 0, 0, 4, 3, 3, 4, 2, 2, 3, 2, 2, 4, 3, 3, 4, 1, 1, 2, 1, 1, 3, 2, 2, 3, 1, 1, 2, 1, 1, 4, 3, 3, 4, 2, 2, 3, 2, 2, 4, 3, 3
(list; graph; listen)
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OFFSET
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0,6
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LINKS
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Michael Gilleland, Some Self-Similar Integer Sequences
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FORMULA
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a(n)=sum(k>=0, floor(2*n/3^k))-2*sum(k>=0, floor(n/3^k)) - Benoit Cloitre (benoit7848c(AT)orange.fr), Aug 26 2003
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MATHEMATICA
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p=3; Array[ If[ Mod[ bi=Binomial[ 2#, # ], p ]==0, Select[ FactorInteger[ bi ], Function[ q, q[ [ 1 ] ]==p ], 1 ][ [ 1, 2 ] ], 0 ]&, 27*3, 0 ]
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PROGRAM
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(PARI) a(n)=valuation(binomial(2*n, n), 3)
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CROSSREFS
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Adjacent sequences: A000986 A000987 A000988 this_sequence A000990 A000991 A000992
Sequence in context: A062979 A114781 A083890 this_sequence A132401 A104273 A051778
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com), R. K. Guy (rkg(AT)cpsc.ucalgary.ca)
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