A248349 Numbers k such that 10^k + 123456789 is prime.

4, 11, 17, 23, 26, 79, 82, 221, 526, 821, 1204, 5392, 13139, 35879, 60991, 77669

Offset

1,1

Comments

a(14) > 20000.

a(17) > 2*10^5. - Robert Price, Oct 26 2019

Links

Table of n, a(n) for n=1..16.

Mathematica

Select[Range[10^4], PrimeQ[10^# + 123456789] &] (* Robert Price, Sep 08 2019 *)

Prog

(PARI) for(n=1, 10^4, if(ispseudoprime(10^n + 123456789), print1(n, ", ")))
(Magma) [n: n in [1..500] | IsPrime(10^n + 123456789)]; // Vincenzo Librandi, Oct 12 2014

Crossrefs

Cf. A248350, A248351, A248352, A050289.

Sequence in context: A038241 A360134 A310561 * A246301 A160907 A003146

Adjacent sequences: A248346 A248347 A248348 * A248350 A248351 A248352

Keyword

nonn,more,hard

Author

Derek Orr, Oct 05 2014

Extensions

a(14)-a(16) from Robert Price, Oct 26 2019

Status

approved