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Search: id:A105574
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| A105574 |
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a(n) is the m-th prime number, where m is the smallest prime factor of n. |
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+0
1
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| 3, 5, 3, 11, 3, 17, 3, 5, 3, 31, 3, 41, 3, 5, 3, 59, 3, 67, 3, 5, 3, 83, 3, 11, 3, 5, 3, 109, 3, 127, 3, 5, 3, 11, 3, 157, 3, 5, 3, 179, 3, 191, 3, 5, 3, 211, 3, 17, 3, 5, 3, 241, 3, 11, 3, 5, 3, 277, 3, 283, 3, 5, 3, 11, 3, 331, 3, 5, 3
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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The smallest prime factor of 5 is 5. Hence a(5) is the 5th prime, which is 11.
The smallest prime factor of 6 is 2. Therefore a(6) = 3.
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MATHEMATICA
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Table[Prime[FactorInteger[n][[1, 1]]], {n, 2, 70}]
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PROGRAM
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(PARI) g(n) = for(x=2, n, print1(prime(sdiv(x))", ")) sdiv(n) = \ The smallest prime divisor of n { local(x); x=ifactor(n); return(x[1]) } ifactor(n, m=0) = \The vector of the integer factors of n with multiplicity. { local(f, j, k, flist); flist=[]; f=Vec(factor(n, m)); for(j=1, length(f[1]), for(k = 1, f[2][j], flist = concat(flist, f[1][j]) ); ); return(flist) }
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CROSSREFS
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Adjacent sequences: A105571 A105572 A105573 this_sequence A105575 A105576 A105577
Sequence in context: A076842 A077862 A134061 this_sequence A105562 A089730 A105445
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KEYWORD
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nonn,less
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AUTHOR
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Cino Hilliard (hillcino368(AT)gmail.com), May 03 2005
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EXTENSIONS
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Edited by Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Jul 25 2007
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