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 A213308 #7 Sep 01 2012 11:47:37 %S A213308 1,4,6,8,9,13,17,22,25,27,29,31,32,33,35,43,47,52,55,57,59,67,71,72, %T A213308 75,77,79,83,97,137,173,223,233,237,313,317,337,353,379,523,537,673, %U A213308 733,737,773,797,1373,3137,3373,3733,3797 %N A213308 Numbers with exactly one nonprime substring (substrings with leading zeros are considered to be nonprime). %C A213308 The sequence is finite. Proof: Each 5-digit number has at least 2 nonprime substrings. Thus, each number with more than 5 digits has >= 2 nonprime substrings, too. Consequently, there is a boundary b<10^4, such that all numbers > b have at least 2 nonprime substrings. %C A213308 The first term is a(1)=1=A213302(1). The last term is a(51)=3797=A213300(1). %H A213308 Hieronymus Fischer, <a href="/A213308/b213308.txt">Table of n, a(n) for n = 1..51</a> %e A213308 a(1)=1, since 1 has one nonprime substring. %e A213308 a(51)=3797, since the only nonprime substring of 3797 is 9. %Y A213308 Cf. A019546, A035232, A039996, A046034, A069489, A085823, A211681, A211682, A211684, A211685. %Y A213308 Cf. A035244, A079307, A213300 - A213321. %K A213308 nonn,fini,base %O A213308 1,2 %A A213308 _Hieronymus Fischer_, Aug 26 2012