OFFSET
1,2
COMMENTS
a(34) > 5*10^5. - Robert Price, Aug 26 2015
For numbers k in this sequence, 2^(k-1)*(2^k+11) has deficiency 12 (see A141549). All terms are odd since 4^n+11 == 1+2 == 0 (mod 3). - M. F. Hasler, Jul 18 2016
LINKS
Henri Lifchitz and Renaud Lifchitz (Editors), Search for 2^n+11, PRP Top Records.
Lei Zhou, Between 2^n and primes. [broken link]
EXAMPLE
k = 1: 2^1 + 11 = 13 is prime.
k = 3: 2^3 + 11 = 19 is prime.
k = 2: 2^2 + 11 = 15 is not prime.
MATHEMATICA
Do[ If[ PrimeQ[2^n + 11], Print[n]], {n, 15250}] (* Robert G. Wilson v, Jan 21 2005 *)
PROG
(PARI) for(n=1, 9e9, ispseudoprime(2^n+11)&&print1(n", ")) \\ M. F. Hasler, Jul 18 2016
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Lei Zhou, Jan 20 2005
EXTENSIONS
a(18)-a(22) from Robert G. Wilson v, Jan 21 2005
a(23)-a(33) from Robert Price, Dec 06 2013
Edited by M. F. Hasler, Jul 18 2016
STATUS
approved