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Search: id:A109043
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| 0, 2, 2, 6, 4, 10, 6, 14, 8, 18, 10, 22, 12, 26, 14, 30, 16, 34, 18, 38, 20, 42, 22, 46, 24, 50, 26, 54, 28, 58, 30, 62, 32, 66, 34, 70, 36, 74, 38, 78, 40, 82, 42, 86, 44, 90, 46, 94, 48, 98, 50, 102, 52, 106, 54, 110, 56, 114, 58, 118, 60, 122, 62, 126, 64, 130, 66, 134
(list; graph; listen)
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OFFSET
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0,2
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FORMULA
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a(n) = n*2/GCD(n, 2).
a(n)=-(n*((-1)^n-3))/2 - Stephen Crowley (crow(AT)crowlogic.net), Feb 11 2007
a(n)=A066043(n), n>1. a(n)=2*A026741(n). O.g.f.: 2x(1+x+x^2)/((1-x)^2*(1+x)^2). [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Aug 20 2008]
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MAPLE
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a:=n->add(2+add((-1)^j, j=1..n), j=2..n):seq(a(n), n=1..69); # [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Dec 13 2008]
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PROGRAM
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(Other) sage: [lcm(n, 2)for n in xrange(0, 68)] # [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jun 07 2009]
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CROSSREFS
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Cf. A109042.
Sequence in context: A061108 A053213 A140524 this_sequence A054585 A046203 A100495
Adjacent sequences: A109040 A109041 A109042 this_sequence A109044 A109045 A109046
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KEYWORD
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nonn,easy
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AUTHOR
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Mitch Harris (Harris.Mitchell(AT)mgh.harvard.edu), Jun 18 2005
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