%I #23 Mar 30 2012 18:53:49

%S 2,57,175,357,381,543,777,903,2379,3027,6807,25823,47047,74333,82621,

%T 136213,153425,163471,194873,230547,257799,259555,265111,269545,

%U 285439,289009,302403,305305,311395,354365,416005,484169,569245,718333,755885,781501,1012505

%N Numbers n for which phi(n)=sigma(n'), where phi is the Euler totient function, sigma is the sum of divisors and n' the arithmetic derivative of n.

%H Donovan Johnson, <a href="/A189057/b189057.txt">Table of n, a(n) for n = 1..300</a>

%e phi(57)=36. 57'=22 and sigma(22)=36

%e phi(1012505)=725760. 1012505'=310156 and sigma(310156)=725760

%p with(numtheory);

%p P:=proc(i)

%p local f, n, p, pfs;

%p for n from 1 by 1 to i do

%p pfs:=ifactors(n)[2];

%p f:=n*add(op(2, p)/op(1, p), p=pfs);

%p if phi(n)=sigma(f) then print(n); fi;

%p od;

%p end:

%p P(1000000)

%Y Cf. A000010, A000203, A003415, A166374, A190402, A190403.

%K nonn

%O 1,1

%A _Paolo P. Lava_, May 17 2011