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 A065989 #10 Aug 02 2025 12:15:13
%S A065989 2,10,14,83,669,720,921,2944,4567
%N A065989 Numbers k such that the first k ternary digits of Pi expressed in decimal forms a prime.
%C A065989 No further terms up to 10000. - _Harvey P. Dale_, Oct 14 2018
%e A065989 The first 10 ternary digits of Pi (A004602) are 1001021101 = 20611 in decimal, which is a prime.
%t A065989 Do[ If[ PrimeQ[ FromDigits[ First[ RealDigits[Pi, 2, n]], 2]], Print[n]], {n, 1, 5000} ]
%t A065989 Module[{nn=4600,pd},pd=RealDigits[Pi,3,nn][[1]];Position[Table[ FromDigits[ Take[ pd,n],3],{n,nn}],_?(PrimeQ[#]&)]]//Flatten (* _Harvey P. Dale_, Oct 14 2018 *)
%Y A065989 Cf. A004602.
%K A065989 base,nonn,more
%O A065989 1,1
%A A065989 _Robert G. Wilson v_, Dec 10 2001