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A064421 Term at which n appears in A064413 (if it begins at 2). 13
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,3
COMMENTS
Every nonnegative number appears here exactly once.
LINKS
J. C. Lagarias, E. M. Rains and N. J. A. Sloane, The EKG sequence, Exper. Math. 11 (2002), 437-446.
MATHEMATICA
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;
Array[a, terms] (* Jean-François Alcover, Aug 30 2018, after Robert G. Wilson v *)
CROSSREFS
Cf. A064413. Equals A064664 - 1.
Sequence in context: A060734 A075594 A076022 * A051494 A262025 A118013
KEYWORD
nonn
AUTHOR
Jonathan Ayres (Jonathan.ayres(AT)btinternet.com), Sep 30 2001
EXTENSIONS
More terms from Naohiro Nomoto, Sep 30 2001
STATUS
approved

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Last modified March 29 08:13 EDT 2024. Contains 371265 sequences. (Running on oeis4.)