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 A139225 #4 Mar 30 2012 17:39:33 %S A139225 2,14,310,5334,22361430,5726491990,91625444694,1537228670661645654, %T A139225 1772303994379887828232566404493432150, %U A139225 127707961738824071529862251643555745658871456065738070,8776024305713098891493168973639040433964428736682367693182293334,9649340769776349618630915417390658987602357538676244438223111363610210030934 %N A139225 M(M-1)/3, where M is Mersenne prime A000668(n). %C A139225 Terms from a(13) on have 314 or more digits and are not listed for that reason. - _R. J. Mathar_, May 11 2008 %F A139225 a(n)=A000668(n)*(A000668(n)-1)/3. %Y A139225 Cf. A000668, A036689, A139115, A139116, A139223, A139224, A139226. %K A139225 nonn %O A139225 1,1 %A A139225 _Omar E. Pol_, May 10 2008 %E A139225 More terms from _R. J. Mathar_, May 11 2008