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 A074341 #13 Apr 07 2025 11:15:28
%S A074341 4,7,9,11,81,87,109,117,123,129,201,389,429,441,771,811,831,1037,1143,
%T A074341 1299,1569,1581,1803,1837,1943,2053,2171,2379,2431,3201,3437,3489,
%U A074341 3723,3841,4289,4801,5523,6249,7083,7467,7749,8171,9073,9333,9683,9781,10833
%N A074341 a(1) = 4; a(n) is smallest number > a(n-1) such that the juxtaposition a(1)a(2)...a(n) is a prime.
%H A074341 Harvey P. Dale, <a href="/A074341/b074341.txt">Table of n, a(n) for n = 1..100</a>
%t A074341 a[1] = 4; 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, 47}] (* _Robert G. Wilson v_ *)
%t A074341 nxt[{j_,a_}]:=Module[{k=a+1},While[!PrimeQ[j*10^IntegerLength[k]+k],k++];{j*10^IntegerLength[k]+k,k}]; NestList[nxt,{4,4},50][[;;,2]] (* _Harvey P. Dale_, Apr 07 2025 *)
%Y A074341 Cf. A033679, A033680, A033681.
%Y A074341 Cf. A069606, A046254, A074336, A074338, A074339, A074340, A074342, A074343, A074344, A074345, A074346.
%K A074341 nonn,base
%O A074341 1,1
%A A074341 _Zak Seidov_, Sep 23 2002
%E A074341 More terms from _Robert G. Wilson v_, Aug 05 2005