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A086571
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a(1)=1, for n>1: a(n) = smallest divisor of n occurring earlier at most once.
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10
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1, 1, 3, 2, 5, 2, 7, 4, 3, 5, 11, 4, 13, 7, 15, 8, 17, 6, 19, 10, 21, 11, 23, 6, 25, 13, 9, 14, 29, 10, 31, 8, 33, 17, 35, 9, 37, 19, 39, 20, 41, 14, 43, 22, 15, 23, 47, 12, 49, 25, 51, 26, 53, 18, 55, 28, 57, 29, 59, 12, 61, 31, 21, 16, 65, 22, 67, 34, 69, 35, 71, 18, 73
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OFFSET
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1,3
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COMMENTS
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LINKS
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EXAMPLE
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a(p) = p for primes p>2;
divisor set of n=12: {1,2,3,4,6,12}, divisors occurring <12: 1=a(1)=a(2), 2=a(4)=a(6), 3=a(3)=a(9) and 4=a(8); as 4 occurs only once a(12)=4.
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MATHEMATICA
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a = {1}; twice = {}; Do[nxt = Complement[Divisors[n], twice][[1]]; If[MemberQ[a, nxt], AppendTo[twice, nxt]]; AppendTo[a, nxt], {n, 2, 10}]; a (* Ivan Neretin, May 28 2015 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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