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

1,2

Comments

Complement of A112588.

Links

Table of n, a(n) for n=1..27.

Eric Weisstein's World of Mathematics, Totient Function

Eric Weisstein's World of Mathematics, Divisor Function

Mathematica

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

Prog

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

Crossrefs

Cf. A020488.

Sequence in context: A124455 A072378 A248888 * A068090 A172121 A094222

Adjacent sequences: A112584 A112585 A112586 * A112588 A112589 A112590

Keyword

nonn,fini,full

Author

Reinhard Zumkeller, Sep 14 2005

Status

approved