A169843 EKG sequence started at 6 instead of 2.

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

Offset

1,1

Comments

A generalization of A064413.

Links

Peter Kagey, Table of n, a(n) for n = 1..10000

Eric Weisstein's World of Mathematics, EKG Sequence

Index entries for sequences related to EKG sequence

Index entries for sequences that are permutations of the natural numbers

Mathematica

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 *)

Prog

(Python)
from math import gcd
def aupton(terms):
  alst, aset = [1, 6], {1, 6}
  for n in range(2, terms+1):
    k = 2
    while True:
      while k in aset: k += 1
      if gcd(alst[-1], k) != 1: alst.append(k); aset.add(k); break
      k += 1
  return alst[1:]
print(aupton(73)) # Michael S. Branicky, Jun 02 2021

Crossrefs

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

Sequence in context: A156590 A135617 A019930 * A329591 A123139 A027599

Adjacent sequences: A169840 A169841 A169842 * A169844 A169845 A169846

Keyword

nonn

Author

T. D. Noe and N. J. A. Sloane, Jun 02 2010

Status

approved