OFFSET
1,2
COMMENTS
Is there some k such that k! + 2^k + 11 and k! + 2^k - 11 are prime?
a(16) > 20000. - Michael S. Branicky, Jul 25 2024
EXAMPLE
For k = 0, k! + 2^k + 11 = 0! + 2^0 + 11 = 13, which is prime.
For k = 3, k! + 2^k - 11 = 3! + 2^3 - 11 = 3, which is prime.
MATHEMATICA
Select[Range[0, 400], Or[PrimeQ[#! + 2^# + 11], PrimeQ[#! + 2^# - 11]] &] (* Michael De Vlieger, Nov 17 2015 *)
Select[Range[0, 500], AnyTrue[#!+2^#+{11, -11}, PrimeQ]&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jul 05 2019 *)
PROG
(PARI) for(n=0, 1e3, if(isprime(n!+2^n-11) || isprime(n!+2^n+11), print1(n", ")))
(PARI) is(n)=my(N=n!+2^n); ispseudoprime(N-11) || ispseudoprime(N+11) \\ Charles R Greathouse IV, Nov 17 2015
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Altug Alkan, Oct 19 2015
EXTENSIONS
a(14) from Charles R Greathouse IV, Nov 17 2015
a(15) from Michael S. Branicky, Jun 17 2023
STATUS
approved