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A086571 a(1)=1, for n>1: a(n) = smallest divisor of n occurring earlier at most once. 10
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,3
COMMENTS
a(A086939(n)) = a(A086938(n)) = n. - Reinhard Zumkeller, Jul 24 2003
LINKS
EXAMPLE
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.
MATHEMATICA
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 *)
CROSSREFS
Sequence in context: A274457 A328579 A046524 * A350509 A133945 A124219
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Jul 22 2003
STATUS
approved

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Last modified March 29 11:45 EDT 2024. Contains 371278 sequences. (Running on oeis4.)