A112587 Numbers m such that phi(m) <= 2*tau(m), where phi=A000010 and tau=A000005.

1, 2, 3, 4, 5, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20, 24, 28, 30, 36, 40, 42, 48, 60, 72, 84, 90, 120

Offset: 1

Author

Reinhard Zumkeller, Sep 14 2005

Keywords

• nonn
• fini
• full

Comments

Complement of A112588.

Links

• Eric Weisstein's World of Mathematics, Totient Function
• Eric Weisstein's World of Mathematics, Divisor Function

Crossrefs

Cf. A020488.

Programs

Mathematica

Select[Range[150],EulerPhi[#]<=2DivisorSigma[0,#]&] (* Harvey P. Dale, Mar 04 2013 *)

PARI

is(n)=eulerphi(n)<=2*numdiv(n) \\ Charles R Greathouse IV, Feb 21 2013