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Search: id:A065393
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| A065393 |
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Sigma[Phi[n]] - Phi[Sigma[n]] is increasing at these values of n. |
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+0
4
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| 3, 5, 7, 11, 13, 17, 19, 29, 31, 37, 41, 53, 61, 73, 95, 97, 109, 127, 143, 157, 181, 209, 241, 287, 313, 323, 337, 377, 403, 407, 421, 473, 527, 533, 541, 589, 601, 661, 713, 731, 757, 779, 899, 1009, 1073, 1147, 1159, 1199, 1271, 1321, 1333, 1349, 1517
(list; graph; listen)
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OFFSET
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1,1
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LINKS
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Harry J. Smith, Table of n, a(n) for n=1,...,500
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FORMULA
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a = 0; s = 0; Do[s = DivisorSigma[1, EulerPhi[n]] - EulerPhi[DivisorSigma[1, n]]; If[s>a, a = s; Print[n]], {n, 1, 10000}]
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EXAMPLE
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First composite number is the 19th term, 143.
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PROGRAM
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(PARI) { n=r=0; for (m=1, 10^9, x=sigma(eulerphi(m)) - eulerphi(sigma(m)); if (x > r, r=x; write("b065393.txt", n++, " ", m); if (n==500, return)) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Oct 18 2009]
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CROSSREFS
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Sigma[Phi[m]]-Phi[Sigma[m]] = A065395[m] = A000203[A000010[m]]-A000010[A000203[m]]. Cf. A000010, A000203, A065394, A065395.
Sequence in context: A059645 A090190 A065041 this_sequence A132143 A045393 A001097
Adjacent sequences: A065390 A065391 A065392 this_sequence A065394 A065395 A065396
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), Nov 05 2001
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