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 A069591 #7 Jun 17 2021 18:47:05
%S A069591 7,71,701,7001,70001,700001,7000003,70000027,700000001,7000000001,
%T A069591 70000000033,700000000009,7000000000009,70000000000009,
%U A069591 700000000000051,7000000000000037,70000000000000003,700000000000000033
%N A069591 Smallest prime in which the n-th significant digit is a 7.
%p A069591 7,seq(nextprime(7*10^j),j=1..32);
%t A069591 Join[{7},NextPrime/@(7*10^Range[20])] (* _Harvey P. Dale_, Jun 17 2021 *)
%Y A069591 Cf. A069588, A069589, A069590.
%K A069591 base,nonn
%O A069591 1,1
%A A069591 _Amarnath Murthy_, Mar 25 2002
%E A069591 More terms from _Sascha Kurz_, Mar 28 2002