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

1,1

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

Mathematica

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

Prog

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

Crossrefs

Cf. A000010, A000203, A084820.

Sequence in context: A357706 A119123 A293625 * A345654 A298462 A066763

Adjacent sequences: A084818 A084819 A084820 * A084822 A084823 A084824

Keyword

nonn

Author

Reinhard Zumkeller, Jun 04 2003

Status

approved