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 A088623 #7 Mar 28 2015 22:12:29
%S A088623 11,0,13,0,0,0,17,0,19,0,114641,0,113,0,0,0,1289,0,1361,0,
%T A088623 11025506433613486607375777617584133309366191904729927960524981845743709132117581,
%U A088623 0,1907846434775996175406740561329,0,0,0,127,0,1500246412961,0,131,0
%N A088623 Prime obtained as the concatenation 1 followed by the smallest power of n, or 0 if no such number exists.
%F A088623 a(2k)=a(5k)=0. - _Ray Chandler_, Oct 23 2003
%t A088623 f[n_] := Block[{k = 1}, While[ p = ToExpression["1" <> ToString[n^k]]; !PrimeQ[p], k++ ]; p]; g[n_] := If[ Mod[n, 10] == 1 || Mod[n, 10] == 3 || Mod[n, 10] == 7 || Mod[n, 10] == 9, f[n], 0]; Table[ g[n], {n, 1, 33}] (* _Robert G. Wilson v_, Oct 31 2003 *)
%Y A088623 Cf. A088622.
%K A088623 base,nonn
%O A088623 1,1
%A A088623 _Amarnath Murthy_, Oct 19 2003
%E A088623 Corrected and extended by _Ray Chandler_, Oct 23 2003