OFFSET
1,2
COMMENTS
Computed by T. D. Noe, Dec 19 2003.
LINKS
Eric Weisstein's World of Mathematics, Modular Prime Counting Function
FORMULA
a(n) = A091116(n) - 1.
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\6-1, isprime(6*k+5)); \\ Jinyuan Wang, Aug 04 2019
CROSSREFS
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
a(16) from Griffin N. Macris, Jan 18 2023
STATUS
approved