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A065393 Sigma(phi(m)) - phi(sigma(m)) is increasing at these values of m. 5
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; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

First composite number is the 15th term, 95. [Corrected by Jacob Vecht, Jul 28 2020]

LINKS

Harry J. Smith, Table of n, a(n) for n = 1..500

MATHEMATICA

a = 0; s = 0; Do[s = DivisorSigma[1, EulerPhi[n]] - EulerPhi[DivisorSigma[1, n]]; If[s>a, a = s; Print[n]], {n, 1, 10000}]

PROG

(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)) ) } \\ Harry J. Smith, Oct 18 2009

CROSSREFS

Cf. A000010, A000203, A065394, A065395.

Sequence in context: A325143 A276357 A065041 * A179740 A186884 A045393

Adjacent sequences:  A065390 A065391 A065392 * A065394 A065395 A065396

KEYWORD

nonn

AUTHOR

Labos Elemer, Nov 05 2001

STATUS

approved

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Last modified May 8 08:51 EDT 2021. Contains 343666 sequences. (Running on oeis4.)