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 A144858 #2 Mar 31 2012 21:08:36 %S A144858 0,1,120,2016,32640,130816,523776,2096128,8386560,134209536,536854528, %T A144858 2147450880,34359607296,549755289600,2199022206976,8796090925056, %U A144858 35184367894528,140737479966720,562949936644096,2251799780130816 %N A144858 Numbers of the form 2^(n-1)*(2^n - 1) which aren't perfect numbers. %C A144858 A006516 with removed A000396. %Y A144858 A006516, A000396 %K A144858 nonn %O A144858 1,3 %A A144858 _Artur Jasinski_, Sep 23 2008