

A135239


Numbers n such that sigma(phi(n))=2n.


1




OFFSET

1,1


COMMENTS

No other terms below 10^10.


LINKS

Table of n, a(n) for n=1..4.


EXAMPLE

sigma(phi(222850677))=sigma(118879488)=445701354=2*222850677, so 222850677 is in the sequence.


MATHEMATICA

Do[If[DivisorSigma[1, EulerPhi[n]]==2n, Print[n]], {n, 420000000}]


CROSSREFS

Cf. A135240.
Sequence in context: A187862 A186864 A338963 * A046043 A138480 A047627
Adjacent sequences: A135236 A135237 A135238 * A135240 A135241 A135242


KEYWORD

more,nonn


AUTHOR

Farideh Firoozbakht, Dec 26 2007


EXTENSIONS

Search extended to 10^10 by Max Alekseyev, Sep 25 2009


STATUS

approved



