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A171911
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Van Eck's sequence (cf. A181391), but starting with a(1) = 1.
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12
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1, 0, 0, 1, 3, 0, 3, 2, 0, 3, 3, 1, 8, 0, 5, 0, 2, 9, 0, 3, 9, 3, 2, 6, 0, 6, 2, 4, 0, 4, 2, 4, 2, 2, 1, 23, 0, 8, 25, 0, 3, 19, 0, 3, 3, 1, 11, 0, 5, 34, 0, 3, 7, 0, 3, 3, 1, 11, 11, 1, 3, 5, 13, 0, 10, 0, 2, 33, 0, 3, 9, 50, 0, 4, 42, 0, 3, 7, 25, 40, 0, 5, 20, 0, 3, 8, 48, 0, 4, 15
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OFFSET
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1,5
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COMMENTS
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After the initial value, the sequence is extended by a(n+1) = min { k > 0: a(n-k) = a(n) } or 0 if no such k exists, i.e., if a(n) did not appear earlier.
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LINKS
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MATHEMATICA
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t = {1};
Do[
d = Quiet[Check[Position[t, Last[t]][[-2]][[1]], 0], Part::partw];
If[d == 0, x = 0, x = Length[t] - d];
AppendTo[t, x], 100]
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PROG
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(Python)
for n in range(1, 10**4):
for m in range(n-1, -1, -1):
l = n-m
break
else: # break did not occur
l = 0
(PARI) A171911_vec(N, a=1, 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
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CROSSREFS
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Cf. A181391, A171912, A171913, A171914, A171915, A171916, A171917, A171918 (same but starting with 0, 2, ..., 8).
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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