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A171918 Van Eck sequence (cf. A181391) starting with a(1) = 8.

%I A171918 #16 Dec 21 2021 12:16:21
%S A171918 8,0,0,1,0,2,0,2,2,1,6,0,5,0,2,6,5,4,0,5,3,0,3,2,9,0,4,9,3,6,14,0,6,3,
%T A171918 5,15,0,5,3,5,2,17,0,6,11,0,3,8,47,0,4,24,0,3,7,0,3,3,1,49,0,5,22,0,3,
%U A171918 7,11,22,5,7,4,20,0,9,46,0,3,12,0,3,3,1,23,0,5,16,0,3,7,19,0,4
%N A171918 Van Eck sequence (cf. A181391) starting with a(1) = 8.
%C A171918 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. - _M. F. Hasler_, Jun 12 2019
%F A171918 a(n+1) = A181391(n) up to the first occurrence of a(1) = 8 in A181391. - _M. F. Hasler_, Jun 15 2019
%o A171918 (PARI) A171918_vec(N,a=8,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 11 2019
%o A171918 (Python)
%o A171918 from itertools import count, islice
%o A171918 def A171918gen():
%o A171918     yield 8
%o A171918     b, bdict = 8, {8:(1,)}
%o A171918     for n in count(2):
%o A171918         if len(l := bdict[b]) > 1:
%o A171918             b = n-1-l[-2]
%o A171918         else:
%o A171918             b = 0
%o A171918         if b in bdict:
%o A171918             bdict[b] = (bdict[b][-1],n)
%o A171918         else:
%o A171918             bdict[b] = (n,)
%o A171918         yield b
%o A171918 A171918_list = list(islice(A171918gen(),30)) # _Chai Wah Wu_, Dec 21 2021
%Y A171918 Cf. A181391, A171911, ..., A171917 (same but starting with 0, 1, ..., 7).
%K A171918 nonn
%O A171918 1,1
%A A171918 _N. J. A. Sloane_, Oct 22 2010
%E A171918 Name edited and cross-references added by _M. F. Hasler_, Jun 12 2019