%I
%S 4,0,0,1,0,2,0,2,2,1,6,0,5,0,2,6,5,4,17,0,6,5,5,1,14,0,6,6,1,5,7,0,6,
%T 5,4,17,17,1,9,0,8,0,2,28,0,3,0,2,5,15,0,4,17,16,0,4,4,1,20,0,5,12,0,
%U 3,18,0,3,3,1,11,0,5,11,3,6,42,0,6,3,5,8,40,0,6,6,1,17,34,0,6
%N Van Eck sequence (cf. A181391) starting with a(1) = 4.
%C A van Eck sequence is defined recursively by a(n+1) = min { k > 0  a(nk) = a(n) } or 0 if this set is empty, i.e., a(n) does not appear earlier in the sequence.  _M. F. Hasler_, Jun 15 2019
%F a(n+1) = A181391(n) up to the first occurrence of a(1) = 4 in A181391.  _M. F. Hasler_, Jun 15 2019
%o (PARI) A171914_vec(N, a=4, i=Map())={vector(N, n, a=if(n>1, iferr(nmapget(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 crossreferences added by _M. F. Hasler_, Jun 15 2019
