%I #10 Dec 24 2021 08:17:23
%S 3,7,19,163,487,1459,39367,86093443,258280327,411782264189299,
%T 116299474006080119380780339,3140085798164163223281069127,
%U 84782316550432407028588866403,20602102921755074907947094535687
%N Primes of the form 2*3^k + 1.
%H Hartosh Singh Bal and Gaurav Bhatnagar, <a href="https://arxiv.org/abs/1903.09619">Prime number conjectures from the Shapiro class structure</a>, arXiv:1903.09619 [math.NT], 2019.
%t Select[2*3^Range[100]+1, PrimeQ]
%Y Cf. A003306 (k such that 2*3^k + 1 is prime), A003307 (k such that 2*3^k - 1 is prime).
%K nonn
%O 1,1
%A _T. D. Noe_, Aug 24 2005