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Search: id:A117982
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| 1, 7, 73, 511, 3577, 37303, 262657, 1838599, 19173961, 134217727, 939524089, 9797894071, 68585258497, 480096809479, 5006723870281, 35253225520639, 246772578644473, 2573485463006647, 18014398643699713, 126100790505897991
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OFFSET
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0,2
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COMMENT
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Divisors of a(9)=2^(3^3)-1=2^27-1 are a(0),a(1),a(2),a(3),a(6),a(7),a(8),a(9). Divisors of a(3)=2^(3^2)-1=2^9-1 are a(0),a(1),a(2),a(3).
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FORMULA
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a(n)=sum{k=0..3n, (-1)^(3n-k)*L(C(3n,k)/3)*2^k} where L(j/p) is the Legendre symbol of j and p.
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CROSSREFS
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Sequence in context: A139966 A027017 A076106 this_sequence A003535 A050917 A025592
Adjacent sequences: A117979 A117980 A117981 this_sequence A117983 A117984 A117985
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KEYWORD
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easy,nonn
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AUTHOR
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Paul Barry (pbarry(AT)wit.ie), Apr 06 2006
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