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A061800
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a(n) =n + (-1)^(n mod 3).
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3
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1, 0, 3, 4, 3, 6, 7, 6, 9, 10, 9, 12, 13, 12, 15, 16, 15, 18, 19, 18, 21, 22, 21, 24, 25, 24, 27, 28, 27, 30, 31, 30, 33, 34, 33, 36, 37, 36, 39, 40, 39, 42, 43, 42, 45, 46, 45, 48, 49, 48, 51, 52, 51, 54, 55, 54, 57, 58, 57, 60, 61, 60, 63, 64, 63, 66, 67, 66, 69, 70, 69, 72
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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LINKS
| Harry J. Smith, Table of n, a(n) for n=0,...,1000
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FORMULA
| O.g.f.: (1-x+3*x^2)/[(-1+x)^2*(1+x+x^2)]. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 02 2008
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EXAMPLE
| a(4) = 4 + (-1)^1 = 3
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PROG
| (PARI) { for (n=0, 1000, write("b061800.txt", n, " ", n + (-1)^(n%3)) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Jul 28 2009]
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CROSSREFS
| Cf. A004442, A014681.
Sequence in context: A074372 A049276 A101684 * A048250 A073181 A183100
Adjacent sequences: A061797 A061798 A061799 * A061801 A061802 A061803
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KEYWORD
| easy,nonn
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AUTHOR
| Olivier Gerard (olivier.gerard(AT)gmail.com), Jun 22 2001
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