A081746 a(1)=1; for n>1, a(n)=a(n-1)-3 if n is already in the sequence, a(n)=a(n-1)+5 otherwise.
1, 6, 11, 16, 21, 18, 23, 28, 33, 38, 35, 40, 45, 50, 55, 52, 57, 54, 59, 64, 61, 66, 63, 68, 73, 78, 83, 80, 85, 90, 95, 100, 97, 102, 99, 104, 109, 106, 111, 108, 113, 118, 123, 128, 125, 130, 135, 140, 145, 142, 147, 144, 149, 146, 143, 148, 145, 150
Offset: 1
Links
- Peter Munn, Table of n, a(n) for n = 1..5000
- 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
a[n_] := a[n] = If[n == 1, 1, If[MemberQ[Array[a, n-1], n], a[n-1] - 3, a[n-1] + 5]]; Array[a, 58] (* Jean-François Alcover, Oct 05 2018 *)
Formula
a(n) - n is periodic with period 648.