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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

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