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A054787
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Earliest sequence with a(a(n))=7n.
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1
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0, 2, 7, 4, 21, 6, 35, 14, 9, 56, 11, 70, 13, 84, 49, 16, 105, 18, 119, 20, 133, 28, 23, 154, 25, 168, 27, 182, 147, 30, 203, 32, 217, 34, 231, 42, 37, 252, 39, 266, 41, 280, 245, 44, 301, 46, 315, 48, 329, 98, 51, 350, 53, 364, 55, 378, 63, 58, 399, 60, 413, 62, 427, 392
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OFFSET
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0,2
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LINKS
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FORMULA
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a(7n)=7*a(n), a(7n+1)=7n+2, a(7n+2)=49n+7, a(7n+3)=7n+4, a(7n+4)=49n+21, a(7n+5)=7n+6, a(7n+6)=49n+35
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MATHEMATICA
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a[n_] := a[n] = Which[ Mod[n, 7] == 0, 7*a[n/7], Mod[n, 7] == 1, n+1, Mod[n, 7] == 2, 7*(n-2)+7, Mod[n, 7] == 3, n+1, Mod[n, 7] == 4, 7*(n-4)+21, Mod[n, 7] == 5, n+1, Mod[n, 7] == 6, 7*(n-6)+35]; a[0] = 0; Table[a[n], {n, 0, 63}] (* Jean-François Alcover, Sep 24 2012 *)
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CROSSREFS
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KEYWORD
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nice,nonn
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AUTHOR
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STATUS
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approved
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