

A056725


Numbers n such that 9*10^n  1 is prime.


16



1, 3, 7, 19, 29, 37, 93, 935, 8415, 9631, 11143, 41475, 41917, 48051, 107663, 212903, 223871, 260253, 364521, 383643, 1009567
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OFFSET

1,2


COMMENTS

Also numbers n such that 8*10^n + 9*R_n is prime, where R_n = 11...1 is the repunit (A002275) of length n.


LINKS

Table of n, a(n) for n=1..21.
Makoto Kamada, Prime numbers of the form 899...999.
Index entries for primes involving repunits


EXAMPLE

1009567 is also a member of this sequence, but its position is presently undetermined: 9 * 10^1009567  1 is prime.  Predrag Kurtovic, Sep 19 2016


MATHEMATICA

Do[ If[ PrimeQ[ 8*10^n + (10^n1)], Print[n]], {n, 1, 6750, 2}]


PROG

(PARI) is(n)=isprime(9*10^n1) \\ Charles R Greathouse IV, Feb 17 2017


CROSSREFS

Cf. A003307, A002235, A046865, A079906, A046866, A001771, A005541, A046867, A079907.
Sequence in context: A186452 A016046 A239219 * A091738 A136054 A006032
Adjacent sequences: A056722 A056723 A056724 * A056726 A056727 A056728


KEYWORD

hard,nonn,more


AUTHOR

Robert G. Wilson v, Aug 11 2000


EXTENSIONS

More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
a(16)a(20) from Kamada data by Robert Price, Oct 19 2014
a(21) from Kamada data by Robert Price, Mar 10 2019


STATUS

approved



