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A121606
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Indices n such that A018910[n] = (Fibonacci[n+3] + 2) are primes.
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1
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1, 2, 5, 11, 19, 37, 73, 85, 155, 193, 227, 233, 257, 785, 797, 1277, 2371, 2771, 4213, 9107
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OFFSET
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1,2
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COMMENTS
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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).
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LINKS
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MATHEMATICA
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Do[f=Fibonacci[n+3]+2; If[PrimeQ[f], Print[n]], {n, 1, 3000}]
Select[Range[10000], PrimeQ[Fibonacci[#+3]+2]&] (* Harvey P. Dale, Jul 01 2019 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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