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%I #13 Dec 29 2019 16:48:10
%S 3,4,7,8,16,26,34,42,78,94,101,107,216,255,543,562,851,981,1099,1528,
%T 1824,1955,2122,2488,2500,15331,15961,24107,24938,26051,58504,61617,
%U 81034,85119,89768,90597,97191,116899,195346
%N Indices of primes in A214831.
%C a(40) > 2*10^5.
%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={1,9,9}; For[n=3, n<=1000, n++, sum=Plus@@a; If[PrimeQ[sum], Print[n]]; a=RotateLeft[a]; a[[3]]=sum]
%t Flatten[Position[LinearRecurrence[{1,1,1},{1,9,9},200000],_?PrimeQ]]-1 (* The prime number at index 195346 (term a(39) of this sequence) has 51699 digits, so this program takes a long time to run. *) (* _Harvey P. Dale_, Dec 29 2019 *)
%Y Cf. A001590, A100683, A231574, A231575, A232542, A214899, A230607, A020992, A232498, A214727, A081172, A214752, A141523, A214825, A235862, A214827, A214828, A214829, A243622, A243623, A214831.
%K nonn
%O 1,1
%A _Robert Price_, Jul 08 2014
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