A079907 Numbers n such that 11*12^n -1 is prime.

1, 2, 21, 25, 33, 54, 78, 235, 1566, 2273, 2310, 4121, 7775, 42249, 105974, 138961

Offset: 1

Author

Robert G. Wilson v, Jan 16 2003

Keywords

• nonn
• hard

Comments

a(17) > 2*10^5. - Robert Price, Mar 20 2015

References

• R. K. Guy, Unsolved Problems in Theory of Numbers, Section A3.

Links

• Steven Harvey, Williams Primes
• H. C. Williams, The primality of certain integers of the form 2Ar^n - 1, Acta Arith. 39 (1981), 7-17.

Crossrefs

Cf. A003307, A002235, A046865, A079906, A046866, A001771, A005541, A056725, A046867.

Programs

Magma

[n: n in [1..600]| IsPrime(11*12^n - 1)]; // Vincenzo Librandi, Mar 21 2015

Mathematica

Do[ If[ PrimeQ[11*12^n - 1], Print[n]], {n, 1, 2000}]
Select[Range[10000], PrimeQ[(11 12^# - 1)] &] (* Vincenzo Librandi, Mar 21 2015 *)

PARI

for(n=1,2000, if(isprime(11*12^n-1),print1(n, ", ")))

Extensions

More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 05 2008

a(13)-a(16) from Robert Price, Mar 20 2015