%I #5 Jul 01 2019 10:29:11

%S 1,2,5,11,19,37,73,85,155,193,227,233,257,785,797,1277,2371,2771,4213,

%T 9107

%N Indices n such that A018910[n] = (Fibonacci[n+3] + 2) are primes.

%C A018910[n] is Pisot sequence L(4,5). Prime Pisot L(4,5) numbers are A018910[a(n)] = Fibonacci[a(n) + 3 ] + 2 = {5,7,23,379,17713,102334157,...} = A121605[n]. Most listed a(n) are prime except a(8),a(9),a(14),a(18).

%t Do[f=Fibonacci[n+3]+2;If[PrimeQ[f],Print[n]],{n,1,3000}]

%t Select[Range[10000],PrimeQ[Fibonacci[#+3]+2]&] (* _Harvey P. Dale_, Jul 01 2019 *)

%Y Cf. A121605, A018910, A048584.

%K nonn

%O 1,2

%A _Alexander Adamchuk_, Aug 09 2006

%E More terms from _Harvey P. Dale_, Jul 01 2019