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 A064119 Numbers k such that the first k digits of the Golden Ratio form a prime. 3
 7, 13, 255, 280, 97241 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS 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

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Last modified November 27 09:19 EST 2021. Contains 349365 sequences. (Running on oeis4.)