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A188719 Number of safe primes < 10^n. 0
2, 7, 25, 115, 670, 4324, 30657, 229568, 1775675, 14156112, 115500275, 960392564 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Number of safe primes with at most n digits; or a(10^n).

LINKS

Table of n, a(n) for n=1..12.

Wikipedia, Safe prime

EXAMPLE

a(10^2) = a(100) = #{5, 7, 11, 23, 47, 59, 83} = 7

CROSSREFS

A156875, A006880, A005385

Sequence in context: A150534 A150535 A076176 * A103465 A103464 A339515

Adjacent sequences:  A188716 A188717 A188718 * A188720 A188721 A188722

KEYWORD

nonn

AUTHOR

Krzysztof Ostrowski, Apr 09 2011

STATUS

approved

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Last modified April 23 13:51 EDT 2021. Contains 343204 sequences. (Running on oeis4.)