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%I #7 Jun 14 2012 01:18:45
%S 2,3,8,9,16,19,24,27,46,68,71,78,107,198,309,377,477,1057,1631,2419,
%T 3974,4293,8247,10513,10709,12011,15042,30543,31607,39664,47552,145858
%N Indices of prime generalized tetranacci numbers, A073817.
%C The sequence of generalized tetranacci numbers is defined as beginning with 1, 3, 7, 15. Subsequent terms are the sum of the previous four terms. Note that the sequence of these generalized tetranacci numbers has many more primes than the tetranacci sequence A000078 (whose prime indices are in A104534).
%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
%t a={-1, -1, -1, 4}; Do[s=Plus@@a; a=RotateLeft[a]; a[[4]]=s; If[PrimeQ[s], Print[n]], {n, 30000}]
%Y Cf. A104576 (indices of prime generalized tribonacci numbers).
%K nonn
%O 1,1
%A _T. D. Noe_, Mar 16 2005
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