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Search: id:A141379
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| A141379 |
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a(n) = the smallest positive integer non-coprime to both n and phi(n), where phi(n) is the number of positive integers that are <= n and are coprime to n. |
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3
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| 6, 2, 10, 2, 14, 2, 3, 2, 22, 2, 26, 2, 6, 2, 34, 2, 38, 2, 3, 2, 46, 2, 5, 2, 3, 2, 58, 2, 62, 2, 6, 2, 10, 2, 74, 2, 3, 2, 82, 2, 86, 2, 3, 2, 94, 2, 7, 2, 6, 2, 106, 2, 5, 2, 3, 2, 118, 2, 122, 2, 3, 2, 10, 2, 134, 2, 6, 2, 142, 2, 146, 2, 5, 2, 14, 2, 158
(list; graph; listen)
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OFFSET
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3,1
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COMMENT
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Apparently, for p > 2 a prime, we have a(p) = 2*p. If n is not a prime, then let q be the smallest prime dividing n. phi(n) then has (q-1) as factor. Therefore (q-1)q is neither coprime to n nor phi(n). Since q is the smallest prime dividing n, we have a(n) < n. - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Jun 29 2008
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FORMULA
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a(n) = A141327(n, A000010(n)).
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MATHEMATICA
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a = {}; For[n = 3, n < 80, n++, i = 2; While[Min[GCD[i, n], GCD[EulerPhi[n], i]] == 1, i++ ]; AppendTo[a, i]]; a - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Jun 29 2008
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CROSSREFS
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Cf. A141327, A141377, A141378.
Sequence in context: A050235 A018801 A055021 this_sequence A100616 A097474 A040035
Adjacent sequences: A141376 A141377 A141378 this_sequence A141380 A141381 A141382
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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), Jun 28 2008
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EXTENSIONS
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More terms from Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Jun 29 2008
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