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Search: id:A064680
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| A064680 |
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Halve an even number - double an odd number. |
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+0
2
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| 2, 1, 6, 2, 10, 3, 14, 4, 18, 5, 22, 6, 26, 7, 30, 8, 34, 9, 38, 10, 42, 11, 46, 12, 50, 13, 54, 14, 58, 15, 62, 16, 66, 17, 70, 18, 74, 19, 78, 20, 82, 21, 86, 22, 90, 23, 94, 24, 98, 25, 102, 26, 106, 27, 110, 28, 114, 29, 118, 30, 122, 31, 126, 32, 130, 33, 134, 34, 138, 35
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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a(a(m)) = m for all m with GCD(m, 4) <= 2.
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LINKS
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Harry J. Smith, Table of n, a(n) for n=1,...,1000
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FORMULA
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a(n) = n * 2^(2 * (n mod 2) - 1)
G.f.: (2+x+2x^2)/(1-x^2)^2.
a(n)a(n+3) = -2 + a(n+1)a(n+2).
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PROGRAM
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(PARI) { for (n = 1, 1000, if (n%2, a=2*n, a=n/2); write("b064680.txt", n, " ", a) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Sep 22 2009]
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CROSSREFS
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Cf. A026741.
Sequence in context: A076891 A071883 A099304 this_sequence A057560 A085592 A089849
Adjacent sequences: A064677 A064678 A064679 this_sequence A064681 A064682 A064683
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KEYWORD
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nonn
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AUTHOR
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Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Oct 16 2001
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