%I #7 Jun 14 2012 01:28:56
%S 3,7,31,127,983,122401,15231991,30341581,60439343,239818559,
%T 235883775871,935968272887,462162688688737,3592979567873032703,
%U 439785318101603999198591,432569613524779275706080077
%N Prime Lucas 7-step numbers, A104621.
%H Tony D. Noe and Jonathan Vos Post, <a href="http://www.cs.uwaterloo.ca/journals/JIS/VOL8/Noe/noe5.html">Primes in Fibonacci n-step and Lucas n-step Sequences,</a> J. of Integer Sequences, Vol. 8 (2005), Article 05.4.4
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Lucasn-StepNumber.html">Lucas n-Step Number</a>
%t a={-1, -1, -1, -1, -1, -1, 7}; lst={}; Do[s=Plus@@a; a=RotateLeft[a]; a[[ -1]]=s; If[PrimeQ[s], AppendTo[lst, s]], {n, 1000}]; lst
%Y Cf. A104622 (indices of prime Lucas 7-step numbers).
%K nonn
%O 1,1
%A _T. D. Noe_, Apr 22 2005