A080579 - OEIS

A080579

a(1)=1; for n>1, a(n)=a(n-1)+1 if n is already in the sequence, a(n)=a(n-1)+4 otherwise.

%I #14 Oct 08 2018 02:39:06

%S 1,5,9,13,14,18,22,26,27,31,35,39,40,41,45,49,53,54,58,62,66,67,71,75,

%T 79,80,81,85,89,93,94,98,102,106,107,111,115,119,120,121,122,126,130,

%U 134,135,139,143,147,148,152,156,160,161,162,166,170,174,175

%N a(1)=1; for n>1, a(n)=a(n-1)+1 if n is already in the sequence, a(n)=a(n-1)+4 otherwise.

%H Reinhard Zumkeller, <a href="/A080579/b080579.txt">Table of n, a(n) for n = 1..10000</a>

%H B. Cloitre, N. J. A. Sloane and M. J. Vandermast, <a href="http://www.cs.uwaterloo.ca/journals/JIS/VOL6/Cloitre/cloitre2.html">Numerical analogues of Aronson's sequence</a>, J. Integer Seqs., Vol. 6 (2003), #03.2.2.

%H B. Cloitre, N. J. A. Sloane and M. J. Vandermast, <a href="http://arXiv.org/abs/math.NT/0305308">Numerical analogues of Aronson's sequence</a> (math.NT/0305308)

%t a[1] = 1; a[n_] := a[n] = If[MemberQ[Array[a, n-1], n], a[n-1]+1, a[n-1]+4]; Array[a, 60] (* _Jean-François Alcover_, Oct 08 2018 *)

%o (Haskell)

%o a080579 n = a080579_list !! (n-1)

%o a080579_list = 1 : f 2 [1] where

%o f x zs@(z:_) = y : f (x + 1) (y : zs) where

%o y = if x `elem` zs then z + 1 else z + 4

%o -- _Reinhard Zumkeller_, Sep 26 2014

%Y Cf. A080455-A080458, A080036, A080037.

%K nonn

%O 1,2

%A _N. J. A. Sloane_, Mar 23 2003