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A191469 Numbers n such that 7^n - 6 is prime. 11
2, 3, 6, 9, 21, 25, 33, 49, 54, 133, 245, 255, 318, 1023, 1486, 3334, 6821, 8555, 11605, 42502, 44409, 90291, 92511, 140303 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(14)=1023 and a(15)=1486 correspond to BPSW strong probable primes (passing Pari's ispseudoprime()). - Joerg Arndt, Jun 06 2011

a(25) > 2*10^5. - Robert Price, Nov 14 2014

LINKS

Table of n, a(n) for n=1..24.

MAPLE

A191469:=n->`if`(isprime(7^n-6), n, NULL): seq(A191469(n), n=1..10^3); # Wesley Ivan Hurt, Nov 14 2014

MATHEMATICA

Select[Range[1, 5000], PrimeQ[7^#-6]&] (* Vincenzo Librandi, Aug 05 2012 *)

PROG

(MAGMA) [n: n in [1..1000]| IsPrime(7^n-6)]

(PARI) for(n=1, 10^6, if(isprime(7^n-6), print1(n, ", ")))

CROSSREFS

Cf. A014224, A059266, A059613, A059614, A095714, A177093.

Cf. A236371, A217131, A191469, A090669, A096305, A217130, A217132, A152213.

Sequence in context: A293606 A185376 A321484 * A091053 A095064 A323144

Adjacent sequences:  A191466 A191467 A191468 * A191470 A191471 A191472

KEYWORD

nonn,hard,more

AUTHOR

Vincenzo Librandi, Jun 06 2011

EXTENSIONS

a(17)-a(23) from Robert Price, Jan 24 2014

a(24) from Robert Price, Nov 14 2014

STATUS

approved

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Last modified May 31 05:50 EDT 2020. Contains 334747 sequences. (Running on oeis4.)