

A215058


Number of primes of the form 1 + b^128 for 1 < b < 10^n.


11




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

Table of n, a(n) for n=1..9.
Yves Gallot, Status of the smallest base values yielding Generalized Fermat primes
Yves Gallot, How many prime numbers appear in a sequence ?
Yves Gallot, A Problem on the Conjecture Concerning the Distribution of Generalized Fermat Prime numbers (a new method for the search for large primes)


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/21, isprime((2*b)^128+1))


CROSSREFS

Cf. A215047, A215048, A215049, A215050, A215051, A215057.
Sequence in context: A293532 A208823 A197913 * A214538 A290882 A197651
Adjacent sequences: A215055 A215056 A215057 * A215059 A215060 A215061


KEYWORD

nonn,more


AUTHOR

Henryk Dabrowski, Aug 01 2012


EXTENSIONS

a(8)a(9) from Kellen Shenton, Aug 10 2020


STATUS

approved



