OFFSET
1,1
COMMENTS
EXAMPLE
Mersenne exponent 7 is in the sequence because sigma(4) = 7.
Mersenne exponent 31 is in the sequence because there are two numbers n (16 and 25) with sigma(n) = 31.
PROG
(Magma) Set(Sort([SumOfDivisors(n): n in[1..10000] | IsPrime((2^SumOfDivisors(n))- 1)]))
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Jaroslav Krizek, Jan 16 2015
STATUS
approved