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A128455 Numbers n such that 9^n - 2 is a prime. 13

%I

%S 1,2,3,11,45,51,260,324,390,393,1112,3092,4445,10373,15861,18528,

%T 97715,112961

%N Numbers n such that 9^n - 2 is a prime.

%C a(19) > 2*10^5. - _Robert Price_, Aug 18 2014

%t Do[ f = 9^n - 2; If[ PrimeQ[ f ], Print[ {n, f} ] ], {n,1,1000} ]

%Y Cf. A084714 = smallest prime of the form (2n-1)^k - 2, or 0 if no such number exists. Cf. A128472 = smallest prime of the form (2n-1)^k - 2 for k>(2n-1), or 0 if no such number exists. Cf. A014224, A109080, A090669, A128457, A128458, A128459, A128460, A128461.

%K hard,more,nonn

%O 1,2

%A _Alexander Adamchuk_, Mar 14 2007

%E 1112 from _Stefan Steinerberger_, May 05 2007

%E More terms from _Ryan Propper_, Jan 12 2008

%E a(15)-a(18) from _Robert Price_, Aug 18 2014

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Last modified February 20 17:04 EST 2020. Contains 332080 sequences. (Running on oeis4.)