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 A138140 #2 Mar 30 2012 17:33:54 %S A138140 2,22,232,2332,23532,235532,2357532,23577532,2357117532,235711117532, %T A138140 23571113117532,2357111313117532,235711131713117532, %U A138140 23571113171713117532,2357111317191713117532,235711131719191713117532 %N A138140 Concatenation of terms of n-th row of the triangle of primes A138139. %C A138140 The first 10 members are palindromes A002113. %e A138140 . %e A138140 n ... a(n) %e A138140 1 ... 2 %e A138140 2 ... 22 %e A138140 3 ... 232 %e A138140 4 ... 2332 %e A138140 5 ... 23532 %e A138140 6 ... 235532 %e A138140 7 ... 2357532 %e A138140 8 ... 23577532 %e A138140 9 ... 2357117532 %e A138140 10 .. 235711117532 %e A138140 11 .. 23571113117532 %Y A138140 Cf. A000040, A089182, A138139. %K A138140 easy,nonn,base %O A138140 1,1 %A A138140 _Omar E. Pol_, Mar 09 2008