OFFSET
1,1
COMMENTS
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