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A066043
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a(1) = 1; for m > 0, a(2m) = 2m, a(2m+1) = 4m+2.
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5
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1, 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, 68
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OFFSET
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1,2
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COMMENTS
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Length of period of sequences r(k,n) = floor(sinh(1)*k!) - n*floor(sinh(1)*k!/n) when n is fixed. - Benoit Cloitre, Jun 22 2003
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LINKS
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Harry J. Smith, Table of n, a(n) for n = 1..1000
Index entries for linear recurrences with constant coefficients, signature (0,2,0,-1).
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FORMULA
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O.g.f.: (x+2x^2+4x^3-x^5)/(1-x^2)^2. - Len Smiley, Dec 05 2001
a(n)*a(n+3) = -4 + a(n+1)*a(n+2).
From Harry J. Smith, Nov 08 2009: (Start)
a(n) = A109043(n), n > 1.
a(n) = 2*A026741(n), n > 1. (End)
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EXAMPLE
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r(k,7) is sequence 1, 2, 0, 0, 1, 6, 1, 1, 3, 2, 2, 3, 5, 0, 1, 2, 0, 0, 1, 6, 1, 1, 3, 2, 2, 3, 5, 0.... which is periodic with period (1, 2, 0, 0, 1, 6, 1, 1, 3, 2, 2, 3, 5, 0) of length 14 = a(7).
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PROG
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(PARI) a(n)=if(n<2, 1, if(n%2, 2*n, n))
(PARI) { for (n=1, 1000, a=if (n>1 && n%2, 2*n, n); write("b066043.txt", n, " ", a) ) } \\ Harry J. Smith, Nov 08 2009
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CROSSREFS
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Sequence in context: A334205 A227389 A015906 * A238642 A145019 A066678
Adjacent sequences: A066040 A066041 A066042 * A066044 A066045 A066046
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KEYWORD
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easy,nonn
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AUTHOR
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George E. Antoniou, Nov 30 2001
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STATUS
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approved
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