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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; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| For n > 0: a(n) = A186421(n) + A186421(n+2).
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LINKS
| Vincenzo Librandi, Table of n, a(n) for n = 0..10000
Index to sequences with linear recurrences with constant coefficients, signature (0,2,0,-1).
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FORMULA
| a(n) = n*2 / GCD(n, 2).
a(n) = -(n*((-1)^n-3))/2 - Stephen Crowley, 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, Aug 20 2008]
a(n) = n*A000034(n). - Paul Curtz, Mar 25 2011
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PROG
| (Sage) [lcm(n, 2) for n in xrange(0, 68)] # [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jun 07 2009]
(MAGMA) [-(n*((-1)^n-3))/2: n in [0..70]]; // Vincenzo Librandi, Aug 12 2011
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CROSSREFS
| Cf. A109042.
Sequence in context: A053213 A140524 A204904 * A054585 A190940 A046203
Adjacent sequences: A109040 A109041 A109042 * A109044 A109045 A109046
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KEYWORD
| nonn,easy
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AUTHOR
| Mitch Harris (Harris.Mitchell(AT)mgh.harvard.edu), Jun 18 2005
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