This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A064119 #18 Feb 16 2025 08:32:45
%S A064119 7,13,255,280,97241
%N A064119 Numbers k such that the first k digits of the Golden Ratio form a prime.
%H A064119 Shyam Sunder Gupta, <a href="http://www.shyamsundergupta.com/">My Contributions in Prime Curios</a>
%H A064119 G. L. Honaker, Jr and Chris Caldwell, <a href="https://t5k.org/curios/page.php?number_id=1206">Prime Curios!</a>
%H A064119 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/ConstantPrimes.html">Constant Primes</a>
%H A064119 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/GoldenRatioDigits.html">Golden Ratio Digits</a>
%H A064119 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/IntegerSequencePrimes.html">Integer Sequence Primes</a>
%H A064119 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Phi-Prime.html">Phi-Prime</a>
%e A064119 a(1)=7 because the 7-digit number 1618033 is prime.
%t A064119 Do[If[PrimeQ[ FromDigits[RealDigits[N[GoldenRatio, n + 10], 10, n][[1]]]], Print[n]], {n, 1, 3000}]
%t A064119 With[{gr=RealDigits[GoldenRatio,10,100000][[1]]},Select[Range[ 100000], PrimeQ[ FromDigits[Take[gr,#]]]&]] (* _Harvey P. Dale_, Jul 24 2016 *)
%Y A064119 Cf. A064117.
%K A064119 base,hard,nonn
%O A064119 1,1
%A A064119 _Shyam Sunder Gupta_, Sep 09 2001
%E A064119 a(5) = 97241 from _Eric W. Weisstein_, Jun 04 2009