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%I #8 Jul 22 2021 01:58:55
%S 2,4,12,16,25,36,48,64,75,80,81,100,112,121,144,162,192,208,225,240,
%T 256,272,289,300,320,324,336,363,368,400,405,448,484,512,529,560,567,
%U 576,592,624,688,700,704,720,729,752,768,784,810,816,841,848,867,900
%N Numbers k such that tau(k) does not divide sigma(k)*phi(k), where tau(k) = A000005(k).
%e tau(400) = 15 = 3*5 does not divide phi(400)*sigma(400) = 153760 = 2^5 * 5 * 31^2.
%o (PARI) isok(n) = sigma(n)*eulerphi(n) % numdiv(n); \\ _Michel Marcus_, Jan 08 2014
%K nonn
%O 1,1
%A _Giovanni Resta_, Feb 13 2006
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