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 A046269 #5 Oct 10 2019 00:35:37 %S A046269 0,3,0,7,0,43,29,7,61,683,9049,71,53,59,7829,4348907,3046721,40163,89, %T A046269 62261467,84401,353203,1381,941,2429536481,288609443,8329,6255974849, %U A046269 876792454961,77364883,113209,3962839,853020188851,555523 %N A046269 Largest prime substring in 3^n (0 if none). %Y A046269 Cf. A046261. %K A046269 nonn %O A046269 0,2 %A A046269 _Patrick De Geest_, Jun 15 1998