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 A165223 #3 May 01 2013 21:12:46 %S A165223 21,217,3937,1040257,1073602561,68718821377,1125897758834689, %T A165223 4951760154835678088235319297, %U A165223 1427247692705959880439315947500961989719490561 %N A165223 Products of 2 successive Mersenne primes. %C A165223 Subsequence of A144856 and of A046528. [From _R. J. Mathar_, Sep 17 2009] %F A165223 a(n)=A000668(n)*A000668(n+1). [From _R. J. Mathar_, Sep 17 2009] %K A165223 nonn %O A165223 1,1 %A A165223 Boris Hostnik (megpplus(AT)siol.net), Sep 08 2009 %E A165223 Extended by _R. J. Mathar_, Sep 17 2009 %E A165223 Offset corrected by _N. J. A. Sloane_, Sep 20 2009