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A053669
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Smallest prime not dividing n.
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28
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2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 7, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 7, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 7, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 5, 2, 3, 2
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OFFSET
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1,1
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COMMENTS
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Smallest prime coprime to n.
Smallest n >= 2 coprime to n.
a(#(p-1)) = a(A034386(p-1)) = p is the first appearance of prime p in sequence.
a(A005408(n)) = 2; for n > 2: a(n) = A112484(n,1). [Reinhard Zumkeller, Sep 23 2011]
Average value is 3.674643966... - Charles R Greathouse IV, Nov 20 2012
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LINKS
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T. D. Noe, Table of n, a(n) for n = 1..10000
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EXAMPLE
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a(60) = 7, since all primes smaller than 7 divide 60 but 7 does not.
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MATHEMATICA
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Table[k := 1; While[Not[GCD[n, Prime[k]] == 1], k++ ]; Prime[k], {n, 1, 60}] - Stefan Steinerberger, Apr 01 2006
With[{prs=Prime[Range[10]]}, Flatten[Table[Select[prs, !Divisible[ n, #]&, 1], {n, 110}]]] (* From Harvey P. Dale, May 03 2012 *)
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PROG
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(Haskell)
a053669 n = head . dropWhile ((== 0) . (mod n)) a000040_list
-- Reinhard Zumkeller, Nov 11 2012
(PARI) a(n)=forprime(p=2, , if(n%p, return(p))) \\ Charles R Greathouse IV, Nov 20 2012
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CROSSREFS
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Cf. A007978, A053670-A053674.
Sequence in context: A029208 A087242 A123556 * A112047 A112048 A060395
Adjacent sequences: A053666 A053667 A053668 * A053670 A053671 A053672
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KEYWORD
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nonn,nice,easy
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AUTHOR
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Henry Bottomley, Feb 15 2000
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EXTENSIONS
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More terms from Andrew Gacek (andrew(AT)dgi.net), Feb 21 2000 and James A. Sellers, Feb 22 2000.
Entry revised by David W. Wilson, Nov 25 2006
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STATUS
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approved
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