A238231 - OEIS

%I #8 Mar 26 2014 06:22:56

%S 376,594,846,1178,1222,46498,65198

%N Numbers n such that if x=phi(n)*tau(n)-sigma(n)-n then n=phi(x)*tau(x)-sigma(x)-x.

%C a(8) > 2*10^9. - _Giovanni Resta_, Mar 26 2014

%e Fixed points: 376,...

%e phi(594) = 180, tau(594) = 16, sigma(594) = 1440 and 180*16 - 1440 - 594 = 846.

%e phi(846) = 276, tau(846) = 12, sigma(846) = 1872 and 276*12 - 1872 - 846 = 594.

%p with(numtheory); P:=proc(q)local a,n;

%p for n from 1 to q do a:=phi(n)*tau(n)-sigma(n)-n;

%p if a>0 and phi(a)*tau(a)-sigma(a)-a=n then print(n);

%p fi; od; end: P(10^6);

%Y Cf. A000005, A000010, A000203, A238225-A238230.

%K nonn,more

%O 1,1

%A _Paolo P. Lava_, Feb 20 2014