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 A127891 #18 Dec 09 2018 02:46:28
%S A127891 2,13,113,1223,12113,121283,1237547,12184967,124536947,1219861613,
%T A127891 12181833347,121339693967,1213536676883,12673876537547,
%U A127891 121848768729173,1275463876537547,12429121339693967,165678739293946997,1276812967623946997,15396334245663786197,315396334245663786197,5918918997653319693967,57686312646216567629137,357686312646216567629137
%N A127891 Smallest n-digit left-truncatable prime.
%C A127891 Ends at a(24) = 357686312646216567629137.
%C A127891 Agrees with A088604 for 24 terms, but this sequence ends there while A088604 continues.
%H A127891 Ray Chandler, <a href="/A127891/b127891.txt">Table of n, a(n) for n = 1..24</a>
%H A127891 I. O. Angell and H. J. Godwin, <a href="http://dx.doi.org/10.1090/S0025-5718-1977-0427213-2">On Truncatable Primes</a>, Math. Comput. 31, 265-267, 1977.
%H A127891 <a href="/index/Tri#tprime">Index entries for sequences related to truncatable primes</a>
%t A127891 grow[p_, digits_] := Select[ Table[ FromDigits[Join[{k}, IntegerDigits[p]]], {k, 1, 9}], PrimeQ[#] && Length[ IntegerDigits[#]] == digits&]; g[1] = {3, 7}; g[n_] := g[n] = grow[#, n]& /@ g[n-1] // Flatten; a[1] = 2; a[n_] := Min[g[n]]; Table[a[n], {n, 1, 24}] (* _Jean-François Alcover_, Aug 05 2013 *)
%Y A127891 Cf. A024785, A050987, A088604, A127892.
%K A127891 base,nonn,fini,full
%O A127891 1,1
%A A127891 _Ray Chandler_, Feb 04 2007