

A253850


Mersenne exponents (A000043) that are the sum of the divisors (A000203) of some n.


2




OFFSET

1,1


COMMENTS

Also primes p that are the sum of the divisors of some n where 2^sigma(n)  1 is a Mersenne prime (A000668).
Intersection of A023195 and A000043.
If a(6) exists, it must be bigger than A000043(43) = 30402457.


LINKS

Table of n, a(n) for n=1..5.


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

Cf. A000043, A000203, A000668, A023195, A253849, A253851.
Sequence in context: A176589 A077314 A069246 * A087578 A023195 A100382
Adjacent sequences: A253847 A253848 A253849 * A253851 A253852 A253853


KEYWORD

nonn,more


AUTHOR

Jaroslav Krizek, Jan 16 2015


STATUS

approved



