%I #8 Nov 25 2013 21:50:04
%S 1,2,3,4,7,11,12,27,32,119,127,136,611,755,872,1676,5363,15623,27564,
%T 42679,54576,74123,91043,104331
%N Indices of prime tribonacci numbers (A100683).
%C a(25) > 2*10^5.
%t a={-1,2,2};Print[1],Print[2];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.
%K nonn
%O 1,2
%A _Robert Price_, Nov 25 2013
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