The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Please make a donation to keep the OEIS running. We are now in our 56th year. In the past year we added 10000 new sequences and reached almost 9000 citations (which often say "discovered thanks to the OEIS"). Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A171913 Van Eck sequence (cf. A181391) starting with a(1) = 3. 1

%I

%S 3,0,0,1,0,2,0,2,2,1,6,0,5,0,2,6,5,4,0,5,3,20,0,4,6,9,0,4,4,1,20,9,6,

%T 8,0,8,2,22,0,4,11,0,3,22,6,12,0,5,28,0,3,8,16,0,4,15,0,3,7,0,3,3,1,

%U 33,0,5,18,0,3,7,11,30,0,5,8,23,0,4,23,3,11,10,0,6,39,0,3,7,18,22

%N Van Eck sequence (cf. A181391) starting with a(1) = 3.

%C A van Eck sequence is defined recursively by a(n+1) = min { k > 0 | a(n-k) = a(n) } or 0 if this set is empty, i.e., a(n) does not appear earlier in the sequence. - _M. F. Hasler_, Jun 12 2019

%F a(n+1) = A181391(n) up to the first occurrence of a(1) = 3 in A181391. - _M. F. Hasler_, Jun 15 2019

%t t = {3};

%t Do[

%t d = Quiet[Check[Position[t, Last[t]][[-2]][[1]], 0]];

%t If[d == 0, x = 0, x = Length[t] - d];

%t AppendTo[t, x], 100]

%t t (* _Horst H. Manninger_, Sep 08 2020 *)

%o (PARI) A171913_vec(N, a=3, i=Map())={vector(N, n, a=if(n>1, iferr(n-mapget(i, a), E, 0)+mapput(i, a, n), a))} \\ _M. F. Hasler_, Jun 15 2019

%Y Cf. A181391, A171911, ..., A171918 (same but starting with 0, 1, ..., 8).

%K nonn

%O 1,1

%A _N. J. A. Sloane_, Oct 22 2010

%E Name edited and cross-references added by _M. F. Hasler_, Jun 15 2019

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 4 21:14 EST 2020. Contains 338938 sequences. (Running on oeis4.)