A253849 -id:A253849 - cp's OEIS frontend

A253850 Mersenne exponents (A000043) that are the sum of the divisors (A000203) of some n.

3, 7, 13, 31, 127

Offset: 1

Jaroslav Krizek, Jan 16 2015

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 greater than A000043(48) = 57885161, and also not equal to any of the Mersenne prime exponents 74207281, 77232917, 82589933, 136279841. - Gord Palameta, Oct 22 2024

			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.

Cf. A000043, A000203, A000668, A023195, A253849, A253851.

Set(Sort([SumOfDivisors(n): n in[1..10000] | IsPrime((2^SumOfDivisors(n))- 1)]));

A253851 Mersenne primes (A000668) of the form 2^sigma(n) - 1 for some n.

Original entry on oeis.org

7, 127, 8191, 2147483647, 170141183460469231731687303715884105727

Offset: 1

Jaroslav Krizek, Jan 16 2015

nonn

Numbers n such that 2^sigma(n) - 1 is a Mersenne primes are given in A253849.
Sequence of corresponding values of sigma(n) are given in A253850 and each term of this sequence must be a prime from the sequence of Mersenne exponents (A000043).
If a(6) exists, it must be bigger than A000668(43) = 2^30402457-1.

			Mersenne prime 2147483647 is in the sequence because there are two numbers n (16 and 25) with 2^sigma(n) - 1 = 2^31 - 1 = 2147483647.

Cf. A000043, A000203, A000668, A023195, A253849, A253850.

Set(Sort([(2^SumOfDivisors(n))-1: n in[1..10000] | IsPrime((2^SumOfDivisors(n))-1)]));

cp's OEIS Frontend

A253850 Mersenne exponents (A000043) that are the sum of the divisors (A000203) of some n.

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A253851 Mersenne primes (A000668) of the form 2^sigma(n) - 1 for some n.

Views

Author

Keywords

Comments

Examples

Crossrefs

Programs

Magma