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Search: id:A132009
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| A132009 |
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a(1) = 1; for n>=2, a(n) = n-th positive integer which is coprime to the largest prime divisor of n. |
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+0
1
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| 1, 3, 4, 7, 6, 8, 8, 15, 13, 12, 12, 17, 14, 16, 18, 31, 18, 26, 20, 24, 24, 24, 24, 35, 31, 28, 40, 32, 30, 37, 32, 63, 36, 36, 40, 53, 38, 40, 42, 49, 42, 48, 44, 48, 56, 48, 48, 71, 57, 62, 54, 56, 54, 80, 60, 65, 60, 60, 60, 74, 62, 64, 73, 127, 70, 72, 68, 72, 72, 81, 72, 107
(list; graph; listen)
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OFFSET
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1,2
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FORMULA
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a(n)=A126572(A006530(n),n). - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Nov 09 2007
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EXAMPLE
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The largest prime dividing 12 is 3. The positive integers which are coprime to 3 are 1,2,4,5,7,8,10,11,13,14,16,17,19,20,... The 12th of these is 17, so a(12) = 17.
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MAPLE
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A126572 := proc(n, k) local f, i ; f := 1 ; for i from 1 do if gcd(i, n) = 1 then if f = k then RETURN(i) ; fi ; f := f+1 ; fi ; od: end: A006530 := proc(n) if n = 1 then 1; else max(seq(op(1, i), i=ifactors(n)[2]) ) ; fi ; end: A132009 := proc(n) local p ; p := A006530(n) ; A126572(p, n) ; end: seq(A132009(n), n=1..100) ; - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Nov 09 2007
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MATHEMATICA
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a = {1}; For[n = 2, n < 70, n++, b = FactorInteger[n][[ -1, 1]]; c = 0; i = 1; While[c < n, If[GCD[i, b] == 1, c++ ]; i++ ]; AppendTo[a, i - 1]]; a - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Nov 04 2007
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CROSSREFS
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Sequence in context: A023888 A117553 A120224 this_sequence A086455 A096842 A147966
Adjacent sequences: A132006 A132007 A132008 this_sequence A132010 A132011 A132012
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet (q1qq2qqq3qqqq(AT)yahoo.com), Oct 29 2007
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EXTENSIONS
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More terms from Stefan Steinerberger (stefan.steinerberger(AT)gmail.com) and R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Nov 04 2007
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