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 A119344 #27 Feb 16 2025 08:33:01
%S A119344 2,3,19,111,116,641,5411,170657
%N A119344 Integer lengths of Theodorus-primes: numbers n such that the concatenation of the first n decimal digits of the Theodorus's constant sqrt(3) is prime.
%H A119344 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/ConstantPrimes.html">Constant Primes</a>
%H A119344 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/IntegerSequencePrimes.html">Integer Sequence Primes</a>
%H A119344 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/TheodorussConstantDigits.html">Theodorus's Constant Digits</a>
%e A119344 sqrt(3) = 1.732050807568877..., so
%e A119344 a(1) = 2 (17 with 2 decimal digits is the 1st prime in the decimal expansion),
%e A119344 a(2) = 3 (173 with 3 decimal digits is the 2nd prime in the decimal expansion).
%t A119344 nn = 1000; digs = RealDigits[Sqrt[3], 10, nn][[1]]; n = 0; t = {}; Do[n = 10*n + digs[[d]]; If[PrimeQ[n], AppendTo[t, d]], {d, nn}]; t (* _T. D. Noe_, Dec 05 2011 *)
%t A119344 Module[{nn=171000,c},c=RealDigits[Sqrt[3],10,nn][[1]];Select[Range[ nn], PrimeQ[ FromDigits[Take[c,#]]]&]] (* _Harvey P. Dale_, May 13 2017 *)
%Y A119344 Cf. A119343 (Theodorus-primes).
%Y A119344 Cf. A002194 (decimal expansion of sqrt(3)).
%K A119344 nonn,more,base,hard
%O A119344 1,1
%A A119344 _Eric W. Weisstein_, May 15 2006
%E A119344 Edited by _Charles R Greathouse IV_, Apr 27 2010
%E A119344 a(8) = 170657 from _Eric W. Weisstein_, Aug 18 2013