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 A216449 #36 Jan 01 2025 09:54:32
%S A216449 15,346,1137,1429,11143,21139,70776,98328
%N A216449 Numbers k such that the first k digits of the string kkkk... correspond to a prime number.
%C A216449 The primality of the numbers corresponding to the first 4 terms has been certified with Primo.
%e A216449 k = 15 is in the sequence since the 15-digit number 151515151515151 is prime.
%t A216449 f[n_]:=Block[{d=IntegerDigits@n},FromDigits@d[[Mod[Range@n - 1,Length@d]+1]]]; Select[Range@1500,PrimeQ@f@# &]
%Y A216449 Subsequence of A171491.
%K A216449 nonn,base,more
%O A216449 1,1
%A A216449 _Giovanni Resta_, Sep 11 2012
%E A216449 a(7)-a(8) from _Michael S. Branicky_, Dec 31 2024