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%I #21 Jun 07 2019 23:47:48
%S 2,4,6,8,10,12,14,16,18,20,22,24,30,32,34,36,40,42,44,46,48,50,54,58,
%T 60,64,66,68,70,72,78,80,84,90,92,94,96,98,100,102,106,108,110,114,
%U 118,120,126,128,130,132,136,138,140,144,150,156,160,162,166,168
%N Numbers k such that sigma(phi(k)) < k.
%C All terms are even. However, sigma(phi(k)) may be equal to k for an odd number k if k+2 is a Fermat prime.
%H Robert Israel, <a href="/A230201/b230201.txt">Table of n, a(n) for n = 1..10000</a>
%p for n do if sigma(phi(n))<n then print{n} fi od:
%t Select[Range[200], DivisorSigma[1, EulerPhi[#]] < # &] (* _T. D. Noe_, Oct 14 2013 *)
%o (PARI) isok(n) = sigma(eulerphi(n)) < n; \\ _Michel Marcus_, Oct 12 2013
%Y Cf. A000010, A000203, A001229, A018784, A062402, A066694, A227011, A227927, A230203.
%K nonn
%O 1,1
%A _Vladimir Letsko_, Oct 11 2013
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