A064475 - OEIS

A064475

Number of odd terms among first n terms of A064413 (if it begins at 2).

0, 0, 0, 1, 2, 2, 2, 2, 3, 4, 4, 4, 5, 6, 6, 6, 6, 6, 7, 8, 9, 9, 10, 11, 11, 11, 12, 13, 13, 13, 13, 14, 15, 15, 15, 16, 17, 18, 18, 18, 18, 19, 20, 20, 20, 20, 20, 20, 21, 22, 22, 23, 24, 24, 24, 25, 26, 26, 26, 27, 28, 28, 28, 28, 28, 29, 30, 31, 31, 31

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OFFSET

2,5

LINKS

Table of n, a(n) for n=2..71.

J. C. Lagarias, E. M. Rains and N. J. A. Sloane, The EKG sequence, arXiv:math/0204011 [math.NT], 2002; Exper. Math. 11 (2002), 437-446.

Index entries for sequences related to EKG sequence

MATHEMATICA

ekg[s_] := Block[{m = s[[-1]], k = 3}, While[MemberQ[s, k] || GCD[m, k] == 1, k++]; Append[s, k]];

EKG = Nest[ekg, {1, 2}, 71] ;

a[n_] := Count[EKG[[2 ;; n]], _?OddQ];

Table[a[n], {n, 2, 71}] (* Jean-François Alcover, Jan 11 2019, after Robert G. Wilson v in A064413 *)