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 A138832 #2 Mar 30 2012 17:33:54 %S A138832 36,728,31496,1278128,819133550336,1310718589869056, %T A138832 524287137438691328,21474836472305843008139952128, %U A138832 23058430092136939512658455991569831744654692615953842176 %N A138832 Concatenation of n-th Mersenne prime A000668(n) and n-th perfect number. %e A138832 a(3)=31496 because A000668(3)=31 and A000396(3)=496. %Y A138832 Cf. A000396, A000668, A138816, A138817, A138818, A138819, A138820, A138821, A138822, A138833. %K A138832 base,nonn %O A138832 1,1 %A A138832 _Omar E. Pol_, Apr 06 2008