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

Terms

a(0) =1a(1) =3a(2) =10a(3) =36a(4) =136a(5) =528a(6) =2080a(7) =8256a(8) =32896a(9) =131328a(10) =524800a(11) =2098176a(12) =8390656a(13) =33558528a(14) =134225920a(15) =536887296a(16) =2147516416a(17) =8590000128a(18) =34359869440a(19) =137439215616a(20) =549756338176