A064421 - OEIS

A064421

Term at which n appears in A064413 (if it begins at 2).

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

1,3

COMMENTS

Every nonnegative number appears here exactly once.

LINKS

Table of n, a(n) for n=1..71.

J. C. Lagarias, E. M. Rains and N. J. A. Sloane, The EKG sequence, Exper. Math. 11 (2002), 437-446.

Index entries for sequences related to EKG sequence

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: A375719 A075594 A076022 * A051494 A262025 A118013

Adjacent sequences: A064418 A064419 A064420 * A064422 A064423 A064424

KEYWORD

nonn

AUTHOR

Jonathan Ayres (Jonathan.ayres(AT)btinternet.com), Sep 30 2001

EXTENSIONS

More terms from Naohiro Nomoto, Sep 30 2001

STATUS

approved