A247963 Numbers n such that 57^n + 2 is prime.

0, 1, 2, 4, 5, 54, 81, 310, 360, 1117, 1410, 3320, 66162

Offset: 1

Author

Vincenzo Librandi, Oct 03 2014

Keywords

• nonn
• more

Comments

Numbers of the form 4*h+3 are not in the sequence, since in this case 57^n+2 is divisible by 5.

Numbers ending with 6 are not in the sequence, since in this case 57^n+2 is divisible by 11.

If n == 10 mod 16, 57^n+2 is divisible by 17. - Derek Orr, Oct 04 2014

a(14) > 2*10^5. - Robert Price, Jun 11 2015

Links

• Henri & Renaud Lifchitz, PRP Top Records: Search for 57^n+2.

Crossrefs

Cf. similar sequences listed in A247957.

Programs

Magma

[n: n in [0..300]| IsPrime( 57^n + 2 )];

Mathematica

Select[Range[0, 2000], PrimeQ[57^# + 2] &]

PARI

for(n=1,10^3,if(ispseudoprime(57^n+2),print1(n,", "))) \\ Derek Orr, Oct 04 2014

Extensions

Edited by Bruno Berselli, Oct 04 2014

a(13) from Robert Price, Jun 11 2015