A278053 Primes p such that sigma(2^(p+1)) is prime.

3, 5, 11, 17, 29, 59, 1277, 4421, 110501, 132047, 20996009, 24036581

Offset: 1

Author

Jaroslav Krizek, Nov 09 2016

Keywords

• hard
• nonn
• more

Comments

Primes in A153798 = A000043 - 2 where A000043 = Mersenne exponents.

Corresponding values of primes q are in A278054.

See A000043 (Mersenne exponents) - numbers n such that sigma(2^(n-1)) is a prime.

Examples

			Prime 11 is in the sequence because sigma(2^(11+1)) = sigma(4096) = 8191 (prime).
		

Crossrefs

Cf. A000043, A000203, A153798, A278054.

Programs

Magma

[n: n in [1..10000] | IsPrime(n) and IsPrime(SumOfDivisors(2^(n+1)))];

Mathematica

(* set the terms in A000043 = lst *) Select[lst, PrimeQ[# - 2] &] (* Robert G. Wilson v, Nov 09 2016 *)

PARI

is(n)=isprime(n) && isprime(n+2) && isprime(2^(n+2)-1) \\ Charles R Greathouse IV, Nov 09 2016