Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #10 Aug 03 2014 14:01:21
%S 2,2,727,79,241,727,823541,5764799,19681,16679880978199,31381059607,
%T 13841287199,42052983462257057,6103515623,4747561509941,
%U 28644003124274380508351359,98526125335693359373,136753052840548005895349735207879,22168378200531005859373
%N Smallest prime of the form k^n-2.
%H Vincenzo Librandi, <a href="/A095304/b095304.txt">Table of n, a(n) for n = 1..200</a>
%e a(7)=7^7-2=823541 is prime whereas 3^7-2=2185 and 5^7-2=78123 are composite.
%t Table[k = 2; While[p = k^n - 2; ! PrimeQ[p], k++]; p, {n, 20}] (* _T. D. Noe_, Apr 03 2012 *)
%Y Cf. A095303 (smallest k such that k^n-2 is prime), A087576 (smallest k such that k^n+2 is prime), A095302 (corresponding primes).
%K nonn
%O 1,1
%A _Hugo Pfoertner_, Jun 01 2004
%E a(2) corrected by _Zak Seidov_, Apr 03 2012