A080590 a(1)=1; for n>1, a(n)=a(n-1)+3 if n is already in the sequence, a(n)=a(n-1)+4 otherwise.
1, 5, 9, 13, 16, 20, 24, 28, 31, 35, 39, 43, 46, 50, 54, 57, 61, 65, 69, 72, 76, 80, 84, 87, 91, 95, 99, 102, 106, 110, 113, 117, 121, 125, 128, 132, 136, 140, 143, 147, 151, 155, 158, 162, 166, 169, 173, 177, 181, 184, 188, 192, 196, 199, 203, 207
Offset: 1
Keywords
Links
- Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
- Benoit Cloitre, A study of a family of self-referential sequences, arXiv:2506.18103 [math.GM], 2025. See p. 9.
- Benoit Cloitre, N. J. A. Sloane and M. J. Vandermast, Numerical analogues of Aronson's sequence, J. Integer Seqs., Vol. 6 (2003), #03.2.2.
- Benoit Cloitre, N. J. A. Sloane and M. J. Vandermast, Numerical analogues of Aronson's sequence, arXiv:math/0305308 [math.NT], 2003.
- Robbert Fokkink and Gandhar Joshi, On Cloitre's hiccup sequences, arXiv:2507.16956 [math.CO], 2025. See p. 3.
Programs
-
Haskell
a080590 n = a080590_list !! (n-1) a080590_list = 1 : f 2 [1] where f x zs@(z:_) = y : f (x + 1) (y : zs) where y = z + (if x `elem` zs then 3 else 4) -- Reinhard Zumkeller, Sep 26 2014
-
Mathematica
a[n_] := a[n] = If[n == 1, 1, If[MemberQ[Array[a, n-1], n], a[n-1]+3, a[n-1]+4]]; Array[a, 56] (* Jean-François Alcover, Oct 05 2018 *)
Comments