A278054 Primes p of the form sigma(2^(q+1)) for some prime q.

31, 127, 8191, 524287, 2147483647, 2305843009213693951

Offset: 1

Author

Jaroslav Krizek, Nov 09 2016

Keywords

• nonn

Comments

The next term is too large to include (see the table).

Corresponding values of primes q are in A278053.

Subsequence of Mersenne primes (A000668).

Examples

			8191 = sigma(2^(q+1)) for prime q = 11.
		

Links

• Jaroslav Krizek, Table of n, a(n) for n = 1..7

Crossrefs

Cf. A000043, A000203, A153798, A278053.

Programs

Magma

[SumOfDivisors(2^(n+1)): n in [1..1000] | IsPrime(n) and IsPrime(SumOfDivisors(2^(n+1)))];

Mathematica

Select[DivisorSigma[1, 2^(# + 1)] & /@ Prime@ Range@ 120, PrimeQ] (* Michael De Vlieger, Nov 10 2016 *)