OFFSET
1,3
COMMENTS
Primes 1 + b^128 are a form of generalized Fermat primes.
It is conjectured that a(n) is asymptotic to 0.0242888*li(10^n)
LINKS
Yves Gallot, How many prime numbers appear in a sequence ?
EXAMPLE
a(3) = 7 because the generalized Fermat numbers F_7(b) where b<10^3 are prime only for b: 120, 190, 234, 506, 532, 548, 960.
PROG
(PARI) a(n) = sum(b=1, 10^n/2-1, isprime((2*b)^128+1))
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Henryk Dabrowski, Aug 01 2012
EXTENSIONS
a(8)-a(9) from Kellen Shenton, Aug 10 2020
STATUS
approved