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A253850 Mersenne exponents (A000043) that are the sum of the divisors (A000203) of some n. 2
3, 7, 13, 31, 127 (list; graph; refs; listen; history; text; internal format)
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

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Last modified February 28 23:08 EST 2020. Contains 332351 sequences. (Running on oeis4.)