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 A068697 #12 Mar 04 2024 22:04:47
%S A068697 3,13,0,23252729,2527293133,0,57911131517,4547495153555759,0,
%T A068697 135791113151719,87899193959799101103105107,0,
%U A068697 23252729313335373941434547,357911131517192123252729,0
%N A068697 Smallest prime which is a concatenation of n consecutive odd numbers. If no such prime exists then 0.
%C A068697 a(3k) = 0.
%H A068697 Sean A. Irvine, <a href="/A068697/b068697.txt">Table of n, a(n) for n = 1..100</a>
%e A068697 a(4) = 23252729 as a concatenation of 23,25,27 and 29. a(3) = 0 for a concatenation of 3 odd numbers is always a multiple of 3.
%t A068697 d[n_]:=IntegerDigits[n]; t={3}; Do[If[Mod[m,3]==0,x=0,k=1; While[!PrimeQ[x=FromDigits[Fold[Join,d[k],Table[d[k+2n],{n,m-1}]]]],k++]]; AppendTo[t,x],{m,2,15}]; t (* _Jayanta Basu_, May 21 2013 *)
%Y A068697 Cf. A052077.
%K A068697 base,nonn
%O A068697 1,1
%A A068697 _Amarnath Murthy_, Mar 03 2002
%E A068697 More terms from _Sascha Kurz_, Mar 26 2002