A064119 Numbers k such that the first k digits of the Golden Ratio form a prime.

7, 13, 255, 280, 97241

Offset

1,1

Links

Table of n, a(n) for n=1..5.

Shyam Sunder Gupta, My Contributions in Prime Curios

G. L. Honaker, Jr and Chris Caldwell, Prime Curios!

Eric Weisstein's World of Mathematics, Constant Primes

Eric Weisstein's World of Mathematics, Golden Ratio Digits

Eric Weisstein's World of Mathematics, Integer Sequence Primes

Eric Weisstein's World of Mathematics, Phi-Prime

Example

a(1)=7 because the 7-digit number 1618033 is prime.

Mathematica

Do[If[PrimeQ[ FromDigits[RealDigits[N[GoldenRatio, n + 10], 10, n][[1]]]], Print[n]], {n, 1, 3000}]
With[{gr=RealDigits[GoldenRatio, 10, 100000][[1]]}, Select[Range[ 100000], PrimeQ[ FromDigits[Take[gr, #]]]&]] (* Harvey P. Dale, Jul 24 2016 *)

Crossrefs

Cf. A064117.

Sequence in context: A317209 A084963 A139188 * A224984 A340473 A228030

Adjacent sequences: A064116 A064117 A064118 * A064120 A064121 A064122

Keyword

base,hard,nonn

Author

Shyam Sunder Gupta, Sep 09 2001

Extensions

a(5) = 97241 from Eric W. Weisstein, Jun 04 2009

Status

approved