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A171915 Van Eck sequence (cf. A181391) starting with a(1) = 5.

%I A171915 #12 Jun 16 2019 18:18:41
%S A171915 5,0,0,1,0,2,0,2,2,1,6,0,5,12,0,3,0,2,9,0,3,5,9,4,0,5,4,3,7,0,5,5,1,
%T A171915 23,0,5,4,10,0,4,3,13,0,4,4,1,13,5,12,35,0,8,0,2,36,0,3,16,0,3,3,1,16,
%U A171915 5,16,2,12,18,0,10,32,0,3,12,7,46,0,5,14,0,3,8,30,0,4,40,0,3,7
%N A171915 Van Eck sequence (cf. A181391) starting with a(1) = 5.
%C A171915 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 15 2019
%H A171915 Chai Wah Wu, <a href="/A171915/b171915.txt">Table of n, a(n) for n = 1..10001</a>
%o A171915 (Python)
%o A171915 A171915_list, l = [5, 0], 0
%o A171915 for n in range(1, 10**4):
%o A171915     for m in range(n-1, -1, -1):
%o A171915         if A171915_list[m] == l:
%o A171915             l = n-m
%o A171915             break
%o A171915     else:
%o A171915         l = 0
%o A171915     A171915_list.append(l) # _Chai Wah Wu_, Jan 02 2015
%o A171915 (PARI) A171915_vec(N, a=5, 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 A171915 Cf. A181391, A171911, ..., A171918 (same but starting with 0, 1, ..., 8).
%K A171915 nonn
%O A171915 1,1
%A A171915 _N. J. A. Sloane_, Oct 22 2010
%E A171915 Name and other sections edited by _M. F. Hasler_, Jun 15 2019