

A287061


Numbers k such that (10^(k+3)*6319 + 863)/9 is prime (k > 0).


0




OFFSET

1,1


COMMENTS

The generated prime numbers are of the form '702'...'1'...'207' ('1' concatenated k times to which the prefix '702' and the suffix '207' are concatenated once).
a(1)..a(7) themselves are primes. a(10) > 80000, if it exists.


LINKS



EXAMPLE

11 is a term as (10^(11+3)*6319 + 863)/9 = 70211111111111207 is prime.
23 is a term because (10^(23+3)*6319 + 863)/9 = 70211111111111111111111111207 is prime.


MATHEMATICA

ParallelMap[ If[ PrimeQ[ (10^(#+3)*6319+863)/9], #, Nothing]&, Range[1000]]


PROG

(PARI) is(n) = ispseudoprime((10^(n+3)*6319+863)/9); \\ Altug Alkan, Jul 23 2017


CROSSREFS



KEYWORD

nonn,base,hard,more


AUTHOR



STATUS

approved



