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 A064119 Numbers n such that first n digits of the Golden Ratio form a prime. 3

%I

%S 7,13,255,280,97241

%N Numbers n such that first n digits of the Golden Ratio form a prime.

%H Shyam Sunder Gupta, <a href="http://www.shyamsundergupta.com/">My Contributions in Prime Curios</a>

%H G. L. Honaker, Jr and Chris Caldwell, <a href="http://primes.utm.edu/curios/page.php?number_id=1206">Prime Curios!</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/ConstantPrimes.html">Constant Primes</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/GoldenRatioDigits.html">Golden Ratio Digits</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/IntegerSequencePrimes.html">Integer Sequence Primes</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Phi-Prime.html">Phi-Prime</a>

%e a(1)=7 because 1618033 is prime.

%t Do[If[PrimeQ[ FromDigits[RealDigits[N[GoldenRatio, n + 10], 10, n][[1]]]], Print[n]], {n, 1, 3000}]

%t With[{gr=RealDigits[GoldenRatio,10,100000][[1]]},Select[Range[ 100000], PrimeQ[ FromDigits[Take[gr,#]]]&]] (* _Harvey P. Dale_, Jul 24 2016 *)

%Y Cf. A064117.

%K base,hard,nonn

%O 1,1

%A _Shyam Sunder Gupta_, Sep 09 2001

%E a(5) = 97241 from _Eric W. Weisstein_, Jun 04 2009

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Last modified February 25 23:44 EST 2020. Contains 332270 sequences. (Running on oeis4.)