A141717 Numbers n such that the set of prime factors of phi(n) is a proper subset of the set of prime factors of n and the set of prime factors of n is a proper subset of the set of prime factors of sigma(n).

24, 40, 96, 234, 360, 384, 540, 600, 640, 936, 1536, 1920, 2016, 2160, 2176, 3000, 3240, 3402, 3744, 4320, 4680, 5760, 6048, 6144, 6318, 6528, 6552, 8640, 9600, 9720, 10240, 10880, 11172, 11466, 13608, 14976, 15000, 17280, 18144, 19584

Offset

1,1

Links

Table of n, a(n) for n=1..40.

Prime Puzzles & Problems Connections, Puzzle 451, Prime factors of n, phi(n) & sigma(n)

Example

The set of prime factors of phi(24)is {2}, the set of prime factors of 24 is {2, 3} and the set of prime factors of sigma(24) is {2, 3, 5} so 24 is in the sequence.

Crossrefs

Sequence in context: A316271 A357699 A328375 * A185742 A286876 A181702

Adjacent sequences: A141714 A141715 A141716 * A141718 A141719 A141720

Keyword

easy,nonn

Author

Farideh Firoozbakht, Aug 22 2008

Status

approved