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

Offset: 1

Author

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

Keywords

• nonn

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.
• Index entries for sequences related to EKG sequence

Crossrefs

Cf. A064413. Equals A064664 - 1.

Programs

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 *)

Extensions

More terms from Naohiro Nomoto, Sep 30 2001