A084821 Odd numbers m such that sigma(m) > m + phi(m), where sigma=A000203 is the divisor sum and phi=A000010 the totient.

15, 45, 63, 75, 105, 135, 165, 189, 195, 225, 231, 255, 273, 285, 297, 315, 345, 357, 375, 399, 405, 429, 435, 441, 465, 483, 495, 525, 555, 567, 585, 609, 615, 645, 651, 675, 693, 705, 735, 765, 777, 795, 819, 825, 855, 861, 885, 891, 903, 915, 945, 975

Offset: 1

Author

Reinhard Zumkeller, Jun 04 2003

Keywords

• nonn

Comments

This sequence is closed under multiplication by odd values, and in particular with multiplication by itself. - Charles R Greathouse IV, Feb 19 2013

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000010, A000203, A084820.

Programs

Mathematica

Select[Range[1, 1000, 2], DivisorSigma[1, #] > EulerPhi[#] + # &] (* Amiram Eldar, Sep 12 2019 *)

PARI

is(n)=n%2 && sigma(n)>eulerphi(n)+n \\ Charles R Greathouse IV, Feb 19 2013