OFFSET
1,1
COMMENTS
There is no further term up to prime(300000000).
EXAMPLE
Let n be a natural number and m=3^n*7*90425537;
then sigma(phi(m)) = sigma(3^(n-1)*2*6*90425536) = sigma(3^n*2^8*677*2087) = sigma(3^n)*8*90425538 = sigma(3^n)*sigma(7)*sigma(90425537) = sigma(3^n*7*90425537) = sigma(m),
hence m is in A033631 and the prime number 90425537 is a term of this sequence.
CROSSREFS
KEYWORD
more,nonn
AUTHOR
Farideh Firoozbakht, Jun 07 2005
STATUS
approved