

A165508


Numbers n such that 10^n + 111 is prime.


1




OFFSET

1,1


COMMENTS

Terms must be congruent to 2 or 4 mod 6. Other than the first term, which produces 10^2 + 111 = 211, these terms produce primes whose decimal representation is 1 <n3 0's> 111 concatenated. These are only known to be highly probable primes for 184 and beyond. No more terms up to 15000.
a(8) > 55000.  Tyler NeSmith, Jul 10 2021


LINKS

Table of n, a(n) for n=1..7.


EXAMPLE

As 10111 = 10^4 + 111 is a prime, 4 is a term.


MATHEMATICA

Select[Range[5200], PrimeQ[10^# + 111] &] (* G. C. Greubel, Oct 21 2018 *)


PROG

(PARI) is(n)=ispseudoprime(10^n+111) \\ Charles R Greathouse IV, Jun 13 2017


CROSSREFS

Cf. A096912, A157711, A062339, A020449, A036929, A161786.
Sequence in context: A012369 A009609 A012367 * A018633 A307556 A018637
Adjacent sequences: A165505 A165506 A165507 * A165509 A165510 A165511


KEYWORD

nonn,more


AUTHOR

Rick L. Shepherd, Sep 21 2009


STATUS

approved



