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 A046273 #10 Oct 10 2019 00:34:52
%S A046273 0,7,0,43,401,7,7649,823,4801,3607,82475249,7326743,41287201,89,
%T A046273 23072849,7561,232930569601,2630513987207,8413597910449,
%U A046273 398895185373143,297612001,558545864083,2988049,3400809163
%N A046273 Largest prime substring in 7^n (0 if none).
%H A046273 Vincenzo Librandi, <a href="/A046273/b046273.txt">Table of n, a(n) for n = 0..200</a>
%t A046273 lpss[n_]:=Module[{idn7=IntegerDigits[7^n]},Max[Select[Flatten[ Table[ FromDigits/@ Partition[idn7,i,1],{i,Length[idn7]}]],PrimeQ]]]; Array[ lpss,25,0]/.-\[Infinity]->0 (* _Harvey P. Dale_, Aug 17 2013 *)
%Y A046273 Cf. A046265.
%K A046273 nonn
%O A046273 0,2
%A A046273 _Patrick De Geest_, Jun 15 1998