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A215701
Number of primes of the form 1 + b^2048 for 1 < b < 10^n.
0
0, 0, 1, 4, 40, 276
OFFSET
1,4
COMMENTS
Primes 1 + b^2048 are a form of generalized Fermat primes.
It is conjectured that a(n) is asymptotic to 0.00352764*li(10^n)
EXAMPLE
a(4) = 4 because the generalized Fermat numbers F_11(b) where b<10^4 are prime only for b = 150, 2558, 4650, 4772.
PROG
(PARI) a(n) = sum(b=1, 10^n/2-1, isprime((2*b)^2048+1))
KEYWORD
nonn
AUTHOR
Henryk Dabrowski, Aug 21 2012
STATUS
approved