a(n) = 2^(n-1)*( 2^n + (-1)^n ).

Terms

a(0) =1a(1) =1a(2) =10a(3) =28a(4) =136a(5) =496a(6) =2080a(7) =8128a(8) =32896a(9) =130816a(10) =524800a(11) =2096128a(12) =8390656a(13) =33550336a(14) =134225920a(15) =536854528a(16) =2147516416a(17) =8589869056a(18) =34359869440a(19) =137438691328a(20) =549756338176