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A061395
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Let p be the largest prime factor of n; if p is the k-th prime then set a(n) = k; a(1) = 0 by convention.
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22
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0, 1, 2, 1, 3, 2, 4, 1, 2, 3, 5, 2, 6, 4, 3, 1, 7, 2, 8, 3, 4, 5, 9, 2, 3, 6, 2, 4, 10, 3, 11, 1, 5, 7, 4, 2, 12, 8, 6, 3, 13, 4, 14, 5, 3, 9, 15, 2, 4, 3, 7, 6, 16, 2, 5, 4, 8, 10, 17, 3, 18, 11, 4, 1, 6, 5, 19, 7, 9, 4, 20, 2, 21, 12, 3, 8, 5, 6, 22, 3, 2, 13, 23, 4, 7, 14, 10, 5, 24, 3, 6, 9, 11, 15
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OFFSET
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1,3
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COMMENTS
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Records occur at the primes. - Robert G. Wilson v, Dec 30 2007.
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LINKS
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Harry J. Smith, Table of n, a(n) for n=1,...,1000
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FORMULA
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A000040(a(n)) = A006530(n); a(n) = A049084(A006530(n)). - Reinhard Zumkeller, May 22 2003
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EXAMPLE
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a(20)=3 since the largest prime factor of 20 is 5, which is the 3rd prime.
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MATHEMATICA
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Insert[Table[PrimePi[FactorInteger[n][[ -1]][[1]]], {n, 2, 120}], 0, 1] - Stefan Steinerberger, Apr 11 2006
f[n_] := PrimePi[ FactorInteger@n][[ -1, 1]]; Array[f, 94] (* Robert G. Wilson v, Dec 30 2007 *)
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PROG
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(PARI) { for (n=1, 1000, if (n==1, a=0, f=factor(n)~; p=f[1, length(f)]; a=primepi(p)); write("b061395.txt", n, " ", a) ) } [From Harry J. Smith, Jul 22 2009]
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CROSSREFS
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Cf. A055396, A061394, A133674.
Sequence in context: A135550 A035491 A108230 * A156061 A225395 A124172
Adjacent sequences: A061392 A061393 A061394 * A061396 A061397 A061398
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KEYWORD
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easy,nice,nonn
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AUTHOR
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Henry Bottomley, Apr 30 2001
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EXTENSIONS
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Definition reworded by N. J. A. Sloane, Jul 01 2008
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STATUS
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approved
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