a(n) is the sum of all integers from 2^(n-2)+1 to 2^(n-1).

Terms

a(0) =2a(1) =7a(2) =26a(3) =100a(4) =392a(5) =1552a(6) =6176a(7) =24640a(8) =98432a(9) =393472a(10) =1573376a(11) =6292480a(12) =25167872a(13) =100667392a(14) =402661376a(15) =1610629120a(16) =6442483712a(17) =25769869312a(18) =103079346176a(19) =412317122560