A063824 - OEIS

%I #18 Dec 08 2023 12:29:19

%S 1,9,81,225,2025,5625,50625,65025,585225,1625625,14630625

%N Numbers k such that sigma(phi(k^3)) = phi(sigma(k^3)).

%t Select[Range[3000000],DivisorSigma[1,EulerPhi[#^3]]==EulerPhi[ DivisorSigma[1,#^3]]&] (* _Harvey P. Dale_, Mar 23 2012 *)

%o (PARI) for(n=1,10^9, if(sigma(eulerphi(n^3))==eulerphi(sigma(n^3)),print(n)))

%Y Cf. A000010, A000203, A000578, A062401, A062402.

%K nonn,more

%O 1,2

%A _Jason Earls_, Aug 20 2001

%E a(11) from _Amiram Eldar_, Dec 08 2023