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A215058 Number of primes of the form 1 + b^128 for 1 < b < 10^n. 11
0, 0, 7, 25, 242, 1933, 16080, 139921, 1234958 (list; graph; refs; listen; history; text; internal format)
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
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
Sequence in context: A208823 A197913 A361777 * A214538 A290882 A197651
KEYWORD
nonn,more
AUTHOR
Henryk Dabrowski, Aug 01 2012
EXTENSIONS
a(8)-a(9) from Kellen Shenton, Aug 10 2020
STATUS
approved

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Last modified March 29 08:13 EDT 2024. Contains 371265 sequences. (Running on oeis4.)