A080901 a(1)=2; for n>1, a(n)=a(n-1)-2 if n is already in the sequence, a(n)=a(n-1)+5 otherwise.

2, 0, 5, 10, 8, 13, 18, 16, 21, 19, 24, 29, 27, 32, 37, 35, 40, 38, 36, 41, 39, 44, 49, 47, 52, 57, 55, 60, 58, 63, 68, 66, 71, 76, 74, 72, 70, 68, 66, 64, 62, 67, 72, 70, 75, 80, 78, 83, 81, 86, 91, 89, 94, 99, 97, 102, 100, 98, 103, 101, 106, 104, 102, 100

Offset: 1

Author

N. J. A. Sloane and Benoit Cloitre, Apr 01 2003

Keywords

• nonn
• easy

Links

• Ivan Neretin, Table of n, a(n) for n = 1..1008
• 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.

Crossrefs

Cf. A080578, A080900, A081745.

Programs

Mathematica

Fold[Append[#1, #1[[-1]] + If[MemberQ[#1, #2], -2, 5]] &, {2}, Range[2, 64]] (* Ivan Neretin, Mar 03 2016 *)

Formula

a(n)-n (n >= 1) (A081745) is periodic with period 168.