A080029 a(n) is taken to be the smallest positive integer not already present which is consistent with the condition "n is a member of the sequence if and only if a(n) is a multiple of 3".

0, 2, 3, 6, 5, 9, 12, 8, 15, 18, 11, 21, 24, 14, 27, 30, 17, 33, 36, 20, 39, 42, 23, 45, 48, 26, 51, 54, 29, 57, 60, 32, 63, 66, 35, 69, 72, 38, 75, 78, 41, 81, 84, 44, 87, 90, 47, 93, 96, 50, 99, 102, 53, 105, 108, 56, 111, 114, 59, 117, 120, 62, 123, 126, 65, 129, 132, 68

Offset

0,2

Links

Michael S. Branicky, Table of n, a(n) for n = 0..9999

B. Cloitre, N. J. A. Sloane and M. J. Vandermast, Numerical analogues of Aronson's sequence, J. Integer Seqs., Vol. 6 (2003), #03.2.2.

B. Cloitre, N. J. A. Sloane and M. J. Vandermast, Numerical analogues of Aronson's sequence, arXiv:math/0305308 [math.NT], 2003.

Formula

a(3m)=6m, a(3m+1)=3m+2, a(3m+2)=6m+3.

Mathematica

{#+1, 2#-1, 2#}[[Mod[ #, 3, 1]]]&/@Range[0, 80]  (* Federico Provvedi, Jun 15 2021 *)

Prog

(Python)
def a(n): m, r = divmod(n, 3); return 3*(2-r%2)*m + (r > 0)*(r+1)
print([a(n) for n in range(68)]) # Michael S. Branicky, Jun 15 2021

Crossrefs

Cf. A079000, A079313, A080030, A080031.

Sequence in context: A119790 A272214 A319785 * A091239 A145110 A257405

Adjacent sequences: A080026 A080027 A080028 * A080030 A080031 A080032

Keyword

easy,nonn

Author

N. J. A. Sloane, Mar 14 2003

Extensions

More terms from Matthew Vandermast, Mar 20 2003

Status

approved