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 A068669 #17 Feb 22 2015 14:56:25
%S A068669 1,2,3,5,7,11,13,17,23,31,37,53,71,73,113,131,137,173,311,313,317,373,
%T A068669 1373,3137
%N A068669 Noncomposite numbers in which every substring is noncomposite.
%C A068669 It is easy to see that this sequence is complete - the only potential 5-digit candidate 31373 is not prime. - _Tanya Khovanova_, Dec 09 2006
%e A068669 137 is a member as all the substrings, i.e. 1, 3, 7, 13, 37, 137, are noncomposite.
%e A068669 All substrings of 3137 are noncomposite numbers: 1, 3, 7, 13, 37, 137, 313, 3137. - _Jaroslav Krizek_, Dec 25 2011
%t A068669 noncompositeQ[n_] := n == 1 || PrimeQ[n]; Reap[ Do[ id = IntegerDigits[n]; lid = Length[id]; test = And @@ noncompositeQ /@ FromDigits[#, 10]& /@ Flatten[ Table[ Take[id, {i, j}], {i, 1, lid}, {j, i, lid}], 1]; If[test, Sow[n]], {n, Join[{1}, Prime /@ Range[10000]]}]][[2, 1]](* _Jean-François Alcover_, May 09 2012 *)
%Y A068669 Cf. A012884, A062115, A202262.
%K A068669 base,nonn,fini,full
%O A068669 1,2
%A A068669 _Amarnath Murthy_, Mar 02 2002
%E A068669 1 added following a redefinition by _Jaroslav Krizek_. - _R. J. Mathar_, Jan 20 2012