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A073508 Number of primes == 9 (mod 10) less than 10^n. 4
0, 5, 38, 303, 2390, 19593, 166032, 1440186, 12711333, 113761326, 1029509896, 9401974132, 86516371101 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

This and the related sequences A073505-A073517 and A006880, A073548-A073565 are included because there is interest in the distribution of primes by their initial or final digits.

LINKS

Table of n, a(n) for n=1..13.

Eric Weisstein's World of Mathematics, Modular Prime Counting Function

FORMULA

A073505(n) + A073506(n) + A073507(n) + a(n) + 2 = A006880(n).

EXAMPLE

a(2) = 5 because there are 5 primes == 9 (mod 10) less than 10^2. They are 19, 29, 59, 79 and 89.

MATHEMATICA

c = 0; k = 9; Do[While[k < 10^n, If[PrimeQ[k], c++ ]; k += 10]; Print[c], {n, 1, 10}]

CROSSREFS

Cf. A006880, A087633, A073505, A073506, A073507, A073509, A073510, A073511, A073512, A073513, A073514, A073515, A073516, A073517.

Sequence in context: A027323 A110079 A110082 * A282964 A247773 A207411

Adjacent sequences:  A073505 A073506 A073507 * A073509 A073510 A073511

KEYWORD

base,nonn,more

AUTHOR

Shyam Sunder Gupta, Aug 14 2002

EXTENSIONS

Edited by Robert G. Wilson v, Oct 03 2002

a(10) from Robert G. Wilson v, Dec 22 2003

a(11)-a(13) from Giovanni Resta, Aug 07 2018

STATUS

approved

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Last modified February 22 05:54 EST 2020. Contains 332116 sequences. (Running on oeis4.)