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%I #13 Apr 16 2024 22:45:57
%S 99,814,1371,2047,2883,5816,6105,6851,10718,16744,19390,19651,20080,
%T 20115,20820,22015,22165,22550,23035,25976,30090,31999,32130,34479,
%U 36492,36865,37043,39942,40347,42591,44475,48667,52377,54213,54321
%N Numbers k such that phi(k)+sigma(k) is a perfect cube.
%H Amiram Eldar, <a href="/A061366/b061366.txt">Table of n, a(n) for n = 1..10000</a>
%e phi(99)+sigma(99) = 60+156 = 216 = 6^3, so 99 is a term of the sequence.
%t Select[Range[10^5], IntegerQ[(EulerPhi[ # ] + DivisorSigma[1, # ])^(1/3)] &]
%o (PARI) isok(n) = ispower(eulerphi(n)+sigma(n), 3); \\ _Michel Marcus_, Sep 28 2019
%Y Cf. A000578, A065387.
%K nonn,changed
%O 1,1
%A _Joseph L. Pe_, Feb 13 2002
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