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%I #11 Sep 17 2023 01:57:36
%S 3,4,5,6,8,10,12,17,32,34,40,48,60,257,512,514,544,640,680,768,816,
%T 960,1020,65537,131072,131074,131584,139264,139808,163840,164480,
%U 174080,174760,196608,197376,208896,209712,245760,246720,261120,262140
%N Numbers k such that usigma(phi(k)) is a prime.
%C The only odd terms below 10^7 are 3, 5, 17, 257 & 65537.
%o (PARI) u(n)=sumdivmult(n, d, if(gcd(d, n/d)==1, d));
%o for(n=1,10^5,if(isprime(u(eulerphi(n))),print1(n,", "))); \\ _Joerg Arndt_, Sep 17 2023
%Y Cf. A062514, A034448, A000010.
%K nonn
%O 1,1
%A _Robert G. Wilson v_, Dec 07 2001
%E Deleted incorrect MMA program. - _N. J. A. Sloane_, Sep 17 2023
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