

A103092


Numbers n such that 9*10^n7 is prime.


1



0, 1, 6, 9, 10, 12, 13, 23, 61, 194, 233, 549, 765, 973, 1061, 1186, 1853, 3713, 6789, 7254, 7765, 9025, 10855, 23640, 31440, 31839, 32287, 120342, 132148
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OFFSET

1,3


COMMENTS

Also numbers n such that 8*10^n + 9*R_n  6 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
a(30) > 2*10^5.  Robert Price, Sep 04 2015


LINKS

Table of n, a(n) for n=1..29.
Makoto Kamada, Prime numbers of the form 899...993.
Index entries for primes involving repunits.


FORMULA

a(n) = A101079(n1) + 1 for n>1.


EXAMPLE

For n=0, 9*10^n7=2 which is prime, so 0 is in the sequence.


MATHEMATICA

Do[ If[ PrimeQ[9*10^n  7], Print[n]], {n, 0, 10000}]


PROG

(MAGMA) [n: n in [0..300]  IsPrime(9*10^n7)]; // Vincenzo Librandi, Sep 05 2015
(PARI) is(n)=ispseudoprime(9*10^n7) \\ Charles R Greathouse IV, Jun 12 2017


CROSSREFS

Cf. A002275, A101079.
Sequence in context: A066385 A226913 A293826 * A104523 A091886 A111774
Adjacent sequences: A103089 A103090 A103091 * A103093 A103094 A103095


KEYWORD

more,nonn


AUTHOR

Robert G. Wilson v, Jan 19 2005


EXTENSIONS

One more term from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
a(23)a(26) from Kamada data by Robert Price, Dec 14 2010
Inserted a(1)=0 by Robert Price, Sep 04 2015
a(28)a(29) from Robert Price, Sep 04 2015


STATUS

approved



