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
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.
Programs
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Mathematica
{#+1,2#-1,2#}[[Mod[ #,3,1]]]&/@Range[0,80] (* Federico Provvedi, Jun 15 2021 *) -
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
Formula
a(3m)=6m, a(3m+1)=3m+2, a(3m+2)=6m+3.
Extensions
More terms from Matthew Vandermast, Mar 20 2003