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 A114783 #9 May 22 2014 10:37:15
%S A114783 0,13,0,17,1111111111111111111,113,1117,11119,1123,1129,131,137,
%T A114783 11111141,111143,11111111111111111111111111111147,1153,11159,11161,
%U A114783 167,1171,173,179,1111183,1111189,197,11111101,1103,11111111111111107,1109
%N A114783 Smallest prime of the form: all ones followed by prime(n). a(n) >prime(n). 0 if no such prime exists.
%C A114783 Prime(n) is all zeros followed by prime(n). This is all ones followed by prime(n). Conjecture: No term is zero except a(1) = a(3) = 0.
%e A114783 a(7) = 1117, as 117 is composite prime(8) = 17.
%t A114783 spf[n_]:=Module[{x=IntegerLength[n]+1,idn=IntegerDigits[n]}, While[ !PrimeQ[ FromDigits[ PadLeft[ idn,x,1]]],x++]; FromDigits[ PadLeft[ idn,x,1]]]; Join[{0,13,0},spf/@Prime[Range[4,30]]] (* _Harvey P. Dale_, May 22 2014 *)
%Y A114783 Cf. A114784.
%K A114783 base,nonn
%O A114783 1,2
%A A114783 _Amarnath Murthy_, Nov 17 2005
%E A114783 More terms from _Joshua Zucker_, May 06 2006