

A091119


Number of primes of the form 6k+5 less than 10^n.


1



1, 12, 86, 616, 4806, 39265, 332383, 2880936, 25424819, 227529386, 2059036143, 18803978496, 173032844824, 1602471005226, 14922285950519
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OFFSET

1,2


COMMENTS

Computed by T. D. Noe, Dec 19 2003.


LINKS

Table of n, a(n) for n=1..15.
Eric Weisstein's World of Mathematics, Modular Prime Counting Function


FORMULA

a(n) = A091116(n)  1.
a(n) = A006880(n)  2  A091115(n).  R. J. Mathar, Jul 20 2007


MATHEMATICA

p = Select[Table[6 i + 5, {i, 0, 10^7}], PrimeQ[#] &]; Table[Count[p, x_ /; x < 10^n], {n, 7}] (* Robert Price, May 29 2019 *)


PROG

(PARI) a(n) = sum(k=0, 10^n\61, isprime(6*k+5)); \\ Jinyuan Wang, Aug 04 2019


CROSSREFS

Cf. A007528, A091116.
Sequence in context: A098206 A104911 A283119 * A243248 A046023 A183721
Adjacent sequences: A091116 A091117 A091118 * A091120 A091121 A091122


KEYWORD

nonn,more


AUTHOR

Eric W. Weisstein, Dec 19 2003


EXTENSIONS

a(10) from Robert G. Wilson v, Dec 22 2003
a(11)a(13) from Jinyuan Wang, Aug 04 2019
a(14)a(15) from Griffin N. Macris, Sep 13 2020


STATUS

approved



