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

Author

Derek Orr, Oct 05 2014

Keywords

• nonn
• more
• hard

Comments

a(14) > 20000.

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

Crossrefs

Cf. A248350, A248351, A248352, A050289.

Programs

Magma

[n: n in [1..500] | IsPrime(10^n + 123456789)]; // Vincenzo Librandi, Oct 12 2014

Mathematica

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

PARI

for(n=1,10^4,if(ispseudoprime(10^n + 123456789),print1(n,", ")))

Extensions

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