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%I #27 Jan 18 2023 16:36:20
%S 1,12,86,616,4806,39265,332383,2880936,25424819,227529386,2059036143,
%T 18803978496,173032844824,1602471005226,14922285950519,139619172018237
%N Number of primes of the form 6k+5 less than 10^n.
%C Computed by _T. D. Noe_, Dec 19 2003.
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/ModularPrimeCountingFunction.html">Modular Prime Counting Function</a>
%F a(n) = A091116(n) - 1.
%F a(n) = A006880(n) - 2 - A091115(n). - _R. J. Mathar_, Jul 20 2007
%t 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 *)
%o (PARI) a(n) = sum(k=0, 10^n\6-1, isprime(6*k+5)); \\ _Jinyuan Wang_, Aug 04 2019
%Y Cf. A007528, A091116.
%K nonn,more
%O 1,2
%A _Eric W. Weisstein_, Dec 19 2003
%E a(10) from _Robert G. Wilson v_, Dec 22 2003
%E a(11)-a(13) from _Jinyuan Wang_, Aug 04 2019
%E a(14)-a(15) from _Griffin N. Macris_, Sep 13 2020
%E a(16) from _Griffin N. Macris_, Jan 18 2023
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