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A165508 Numbers n such that 10^n + 111 is prime. 1
2, 4, 184, 460, 784, 3248, 5194 (list; graph; refs; listen; history; text; internal format)
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 <n-3 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

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Last modified September 16 07:19 EDT 2021. Contains 347469 sequences. (Running on oeis4.)