A067193 Numbers k such that sigma(k) == 4 (mod phi(k)).

24, 27, 44, 66, 75, 170, 944, 1200, 16064, 260864, 4189184, 17179541504, 274876596224

Offset: 1

Author

Benoit Cloitre, Feb 19 2002

Keywords

• nonn
• more

Comments

a(14) > 10^12. 1125899822956544 and 4611686013058678784 are also terms. - Donovan Johnson, Feb 29 2012

a(14) > 10^13. If 2^j-5 is prime (A059608) and j > 3, then 2^(j-2)*(2^j-5) is a term. - Giovanni Resta, Mar 29 2020

Crossrefs

Cf. A063514, A059608, A067192.

Extensions

a(11) from Donovan Johnson, Dec 14 2009

a(12)-a(13) from Donovan Johnson, Feb 29 2012