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%I #21 Aug 02 2023 18:44:47
%S 3,5,7,11,13,17,19,29,31,37,41,53,61,73,95,97,109,127,143,157,181,209,
%T 241,287,313,323,337,377,403,407,421,473,527,533,541,589,601,661,713,
%U 731,757,779,899,1009,1073,1147,1159,1199,1271,1321,1333,1349,1517
%N Sigma(phi(m)) - phi(sigma(m)) is increasing at these values of m.
%C First composite number is the 15th term, 95. [Corrected by _Jacob Vecht_, Jul 28 2020]
%H Harry J. Smith, <a href="/A065393/b065393.txt">Table of n, a(n) for n = 1..500</a>
%t a = 0; s = 0; Do[s = DivisorSigma[1, EulerPhi[n]] - EulerPhi[DivisorSigma[1, n]]; If[s>a, a = s; Print[n]], {n, 1, 10000}]
%t DeleteDuplicates[Table[{m,DivisorSigma[1,EulerPhi[m]]-EulerPhi[DivisorSigma[1,m]]},{m,1600}],GreaterEqual[#1[[2]],#2[[2]]]&][[;;,1]] (* _Harvey P. Dale_, Aug 02 2023 *)
%o (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
%Y Cf. A000010, A000203, A065394, A065395.
%K nonn
%O 1,1
%A _Labos Elemer_, Nov 05 2001
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