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 A074345 #14 Jan 26 2022 18:26:53
%S A074345 9,11,21,33,39,71,73,81,101,123,193,257,271,293,379,387,407,627,669,
%T A074345 931,1073,1179,1273,1481,2587,2627,2923,3063,3617,3931,4073,4093,4199,
%U A074345 4491,4801,5387,5647,5739,5859,5979,6149,6369,7527,8053,8207,8647,8949,8981
%N A074345 a(1) = 9; a(n) is smallest number > a(n-1) such that the juxtaposition a(1)a(2)...a(n) is a prime.
%H A074345 Harvey P. Dale, <a href="/A074345/b074345.txt">Table of n, a(n) for n = 1..200</a>
%t A074345 a[1] = 9; a[n_] := a[n] = Block[{k = a[n - 1] + 1 + Mod[a[n - 1], 2], c = IntegerDigits @ Table[ a[i], {i, n - 1}]}, While[ !PrimeQ[ FromDigits @ Flatten @ Append[c, IntegerDigits[k]]], k += 2]; k]; Table[ a[n], {n, 48}] (* _Robert G. Wilson v_ *)
%t A074345 nxt[{j_,a_}]:=Module[{c=a+2},While[CompositeQ[j*10^IntegerLength[c]+c],c+=2];{j*10^IntegerLength[c]+c,c}]; NestList[nxt,{9,9},50][[All,2]] (* _Harvey P. Dale_, Jan 26 2022 *)
%Y A074345 Cf. A046259, A069611, A074336, A074338, A074339, A074340, A074341, A074342, A074343, A074344, A074346.
%K A074345 nonn,base
%O A074345 1,1
%A A074345 _Zak Seidov_, Sep 23 2002
%E A074345 Corrected and extended by _Robert G. Wilson v_, Aug 05 2005