Partial sums of floor(2^n/3).

Terms

a(0) =0a(1) =1a(2) =3a(3) =8a(4) =18a(5) =39a(6) =81a(7) =166a(8) =336a(9) =677a(10) =1359a(11) =2724a(12) =5454a(13) =10915a(14) =21837a(15) =43682a(16) =87372a(17) =174753a(18) =349515a(19) =699040a(20) =1398090a(21) =2796191a(22) =5592393a(23) =11184798a(24) =22369608a(25) =44739229a(26) =89478471a(27) =178956956a(28) =357913926a(29) =715827867