

A102740


Numbers k such that 7*10^k  11 is prime.


0



1, 6, 7, 9, 10, 11, 16, 42, 53, 78, 321, 699, 1858, 3425, 4899, 5734, 11081, 11675, 12136, 14056, 16074, 77969, 158465
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OFFSET

1,2


COMMENTS

a(24) > 2*10^5.
Numbers corresponding to terms <= 699 are certified primes.  Klaus Brockhaus, Feb 15 2005
For k>1, numbers such that the digit 6 followed by k2 occurrences of the digit 9 followed by the digits 89 is prime (see Example section).


LINKS

Table of n, a(n) for n=1..23.
Makoto Kamada, Factorization of nearrepdigitrelated numbers.
Makoto Kamada, Search for 69w89.


EXAMPLE

Initial terms and primes associated:
a(1) = 1, 59;
a(2) = 6, 6999989;
a(3) = 7, 69999989;
a(4) = 9, 6999999989;
a(5) = 10, 69999999989; etc.


MATHEMATICA

Select[Range[1, 100000], PrimeQ[7*10^#  11] &]


PROG

(PARI) is(n)=ispseudoprime(7*10^n  11) \\ Charles R Greathouse IV, Jun 13 2017


CROSSREFS

Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.
Sequence in context: A094868 A131956 A205720 * A248178 A284094 A120183
Adjacent sequences: A102737 A102738 A102739 * A102741 A102742 A102743


KEYWORD

more,nonn


AUTHOR

Tom Mueller (muel4503(AT)unitrier.de), Feb 08 2005


EXTENSIONS

a(11)a(13) from Klaus Brockhaus, Feb 15 2005
a(14)a(22) from Robert Price, Oct 29 2017
a(23) from Robert Price, Jun 21 2019


STATUS

approved



