Many excellent designs for a new banner were submitted. We will use the best of them in rotation.
%N Let A181741(n)=2^(t(n))-2^(k(n))-1, where k(n)>=1, t(n)>=k(n)+1. Then a(n)=t(n).
%Y Cf. A181741
%A _Vladimir Shevelev_, Nov 08 2010