
OFFSET

1,1


COMMENTS

A subsequence of A093034.
If p is a term of this sequence then for each positive integer k, x=p^k
is a solution for the equation sigma(phi(x))=3(x1). See comment lines of
the sequence A093034.


LINKS

Table of n, a(n) for n=1..2.
Achim Flammenkamp, The Multiply Perfect Numbers Page


EXAMPLE

p=673 is prime and sigma(p1)/(p1)=3, so p is in the sequence.


CROSSREFS

Cf. A005820, A093034, A171263, A171264, A171265.
Sequence in context: A297123 A160209 A234117 * A267818 A158392 A264328
Adjacent sequences: A171263 A171264 A171265 * A171267 A171268 A171269


KEYWORD

fini,full,nonn,bref


AUTHOR

M. F. Hasler and Farideh Firoozbakht, Apr 15 2010


STATUS

approved

