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Numbers k such that sigma(k) and phi(k) are both perfect cubes.
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%I #12 Jul 22 2021 01:57:37

%S 1,300118,2250885,5294800,76336260,141483384,242375035,453280968,

%T 456345036,461356896,478240392,537375930,1139523375,1180718238,

%U 1227111595,1599634410,5043835125,5229921340,5610392513,6087775939,6376494509,11038341720,11044670824

%N Numbers k such that sigma(k) and phi(k) are both perfect cubes.

%C phi(k) = A000010(k) is the Euler totient function, while sigma(k) = A000203(k) is the sum of divisors of k.

%C Intersection of A020477 and A039771. - _Michel Marcus_, Jan 04 2014

%e sigma(2250885) = 168^3 and phi(2250885) = 96^3.

%o (PARI) for(n=1, 10^9, if(ispower(eulerphi(n),3), if(ispower(sigma(n),3), print1(n ", ")))) \\ _Donovan Johnson_, Jan 04 2014

%Y Cf. A000010, A000203.

%K nonn

%O 1,2

%A _Giovanni Resta_, Jan 31 2006

%E a(7)-a(20) from _Donovan Johnson_, Feb 06 2010

%E a(21)-a(23) from _Donovan Johnson_, Jan 04 2014