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A278053
Primes p such that sigma(2^(p+1)) is prime.
1
3, 5, 11, 17, 29, 59, 1277, 4421, 110501, 132047, 20996009, 24036581
OFFSET
1,1
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.
EXAMPLE
Prime 11 is in the sequence because sigma(2^(11+1)) = sigma(4096) = 8191 (prime).
MATHEMATICA
(* set the terms in A000043 = lst *) Select[lst, PrimeQ[# - 2] &] (* Robert G. Wilson v, Nov 09 2016 *)
PROG
(Magma) [n: n in [1..10000] | IsPrime(n) and IsPrime(SumOfDivisors(2^(n+1)))]
(PARI) is(n)=isprime(n) && isprime(n+2) && isprime(2^(n+2)-1) \\ Charles R Greathouse IV, Nov 09 2016
CROSSREFS
KEYWORD
hard,nonn,more
AUTHOR
Jaroslav Krizek, Nov 09 2016
STATUS
approved