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Indices of primes in the tribonacci-like sequence, A081172.
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%I #8 Jan 09 2014 17:18:50

%S 3,4,5,9,12,16,24,32,101,116,245,34553,52517,99245,140197

%N Indices of primes in the tribonacci-like sequence, A081172.

%C a(16) > 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, 1, 0}; For[n=3, n<=1000, n++, sum=Plus@@a; If[PrimeQ[sum], Print[n]]; a=RotateLeft[a]; a[[3]]=sum]

%Y Cf. A001590, A100683, A231574, A231575, A232542, A214899, A230607, A020992, A232498, A214727, A081172, A214752.

%K nonn

%O 1,1

%A _Robert Price_, Jan 09 2014