A121606 - OEIS

A121606

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

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

1,2

COMMENTS

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).

LINKS

Table of n, a(n) for n=1..20.

MATHEMATICA

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 *)

CROSSREFS

Cf. A121605, A018910, A048584.

Sequence in context: A319859 A156768 A134694 * A166164 A097008 A276591

Adjacent sequences: A121603 A121604 A121605 * A121607 A121608 A121609

KEYWORD

nonn

AUTHOR

Alexander Adamchuk, Aug 09 2006

EXTENSIONS

More terms from Harvey P. Dale, Jul 01 2019

STATUS

approved