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%I #26 Nov 09 2023 11:25:22
%S 5,23,239,10460353199,617673396283943,450283905890997359,
%T 36472996377170786399,19383245667680019896796719,
%U 67585198634817523235520443624317919,1546132562196033993109383389296863818106322565999
%N Primes of the form 3^k - 4.
%C The next term, a(11), has 84 digits. - _Harvey P. Dale_, Jul 24 2011
%H Vincenzo Librandi, <a href="/A156555/b156555.txt">Table of n, a(n) for n = 1..17</a>
%H F. Firoozbakht, M. F. Hasler, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL13/Hasler/hasler2.html">Variations on Euclid's formula for Perfect Numbers</a>, JIS 13 (2010) #10.3.1
%H Henri & Renaud Lifchitz, <a href="http://www.primenumbers.net/prptop">PRP Records</a>
%H OpenPFGW Project, <a href="http://sourceforge.net/projects/openpfgw/">Primality Tester</a>
%F a(n) = 3^A058959(n) - 4. - _M. F. Hasler_, Oct 31 2009
%e a(1) = 3^2 - 4 = 5 is the smallest prime of that form. - _M. F. Hasler_, Oct 31 2009
%t Select[3^Range[200]-4,PrimeQ] (* _Harvey P. Dale_, Jul 24 2011 *)
%o (PARI) for( k=2,999, is/*pseudo*/prime( p=3^k-4 ) & print1(p", ")) \\ _M. F. Hasler_, Oct 31 2009
%Y Cf. A000040, A058959 (corresponding k's).
%K nonn
%O 1,1
%A _Vincenzo Librandi_, Feb 10 2009
%E a(5) corrected by _M. F. Hasler_, Oct 31 2009
%E a(10) from _Harvey P. Dale_, Jul 24 2011
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