A118841 Numbers k such that ceiling(phi^k) is prime.

1, 2, 3, 4, 8, 16

Offset

1,2

Comments

a(7) if it exists is greater than 250000. - Mark Rodenkirch, Feb 22 2020

Links

Table of n, a(n) for n=1..6.

Eric Weisstein's World of Mathematics, Phi-Prime

Mathematica

Select[Range[20], PrimeQ[Ceiling[GoldenRatio^#]]&] (* James C. McMahon, Sep 14 2024 *)

Prog

(PARI) c(n) = 3*fibonacci(n-1) + fibonacci(n-2) + (n % 2); \\ A169986(n) for n >= 1
for(n=1, 10^7, if(ispseudoprime(c(n)), print1(n, ", ")))
\\ Joerg Arndt, Feb 22 2020

Crossrefs

Cf. A118842, A001606.

Sequence in context: A364595 A352817 A189740 * A126294 A339973 A224912

Adjacent sequences: A118838 A118839 A118840 * A118842 A118843 A118844

Keyword

nonn

Author

Eric W. Weisstein, May 01 2006

Extensions

a(7)-a(8) from Charles R Greathouse IV, Jul 30 2011

a(9)-a(11) from Charles R Greathouse IV, Aug 01 2011

Incorrect a(7)-a(11) removed by Mark Rodenkirch, Feb 22 2020

Status

approved