OFFSET
1,1
COMMENTS
The next terms are > 1.5*10^6.
Contains exactly the halved even terms of A247952.
FORMULA
a(n) = A247952(n)/2. - Elmo R. Oliveira, Nov 28 2023
EXAMPLE
For k = 18, 4^18 + 31 = 68719476767 is prime.
MATHEMATICA
Select[Range[0, 250000], PrimeQ[4^# + 31] &]
PROG
(Magma) [n: n in [0..700] | IsPrime(4^n+31)]; // Vincenzo Librandi, Oct 06 2015
(PARI) for(n=1, 1e3, if(isprime(4^n+31), print1(n", "))) \\ Altug Alkan, Oct 06 2015
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Robert Price, Oct 05 2015
EXTENSIONS
a(11) derived from A247952 by Elmo R. Oliveira, Nov 28 2023
STATUS
approved