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EKG sequence started at 6 instead of 2.
13

%I #21 Jun 02 2021 07:18:51

%S 6,2,4,8,10,5,15,3,9,12,14,7,21,18,16,20,22,11,33,24,26,13,39,27,30,

%T 25,35,28,32,34,17,51,36,38,19,57,42,40,44,46,23,69,45,48,50,52,54,56,

%U 49,63,60,55,65,70,58,29,87,66,62,31,93,72,64,68,74,37,111,75,78,76,80,82,41

%N EKG sequence started at 6 instead of 2.

%C A generalization of A064413.

%H Peter Kagey, <a href="/A169843/b169843.txt">Table of n, a(n) for n = 1..10000</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/EKGSequence.html">EKG Sequence</a>

%H <a href="/index/Ed#EKG">Index entries for sequences related to EKG sequence</a>

%H <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a>

%t f[s_List] := Block[{m = s[[-1]], k = 3}, While[MemberQ[s, k] || GCD[m, k] == 1, k++]; Append[s, k]]; Nest[f, {6, 2}, 71] (* _Michael De Vlieger_, Jan 21 2016, after _Robert G. Wilson v_ at A064413 *)

%o (Python)

%o from math import gcd

%o def aupton(terms):

%o alst, aset = [1, 6], {1, 6}

%o for n in range(2, terms+1):

%o k = 2

%o while True:

%o while k in aset: k += 1

%o if gcd(alst[-1], k) != 1: alst.append(k); aset.add(k); break

%o k += 1

%o return alst[1:]

%o print(aupton(73)) # _Michael S. Branicky_, Jun 02 2021

%Y For other initial terms, see A064413, A169837, A169839, A169841, A169845, A169847, A169849, A169851, A169853, A169855.

%K nonn

%O 1,1

%A _T. D. Noe_ and _N. J. A. Sloane_, Jun 02 2010