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A064421
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Term at which n appears in A064413 (if it begins at 2).
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13
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0, 1, 4, 2, 9, 3, 13, 7, 5, 8, 19, 6, 27, 12, 10, 16, 32, 11, 36, 17, 14, 18, 42, 15, 23, 26, 21, 25, 56, 22, 60, 30, 20, 31, 24, 29, 66, 35, 28, 39, 73, 34, 80, 40, 38, 41, 88, 44, 49, 45, 33, 46, 99, 47, 52, 48, 37, 55, 106, 51, 114, 59, 50, 63, 53, 58, 127, 64, 43, 54, 133
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OFFSET
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1,3
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COMMENTS
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Every nonnegative number appears here exactly once.
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LINKS
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J. C. Lagarias, E. M. Rains and N. J. A. Sloane, The EKG sequence, Exper. Math. 11 (2002), 437-446.
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MATHEMATICA
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terms = 100;
ekg[s_] := Block[{m = s[[-1]], k = 3}, While[MemberQ[s, k] || GCD[m, k] == 1, k++]; Append[s, k]];
EKG = Nest[ekg, {2, 4}, 2 terms];
a[1] = 0; a[n_] := FirstPosition[EKG, n] // First;
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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Jonathan Ayres (Jonathan.ayres(AT)btinternet.com), Sep 30 2001
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EXTENSIONS
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STATUS
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approved
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