a(n) = 2^(n-1)*(2^n+3).

Terms

a(0) =2a(1) =5a(2) =14a(3) =44a(4) =152a(5) =560a(6) =2144a(7) =8384a(8) =33152a(9) =131840a(10) =525824a(11) =2100224a(12) =8394752a(13) =33566720a(14) =134242304a(15) =536920064a(16) =2147581952a(17) =8590131200a(18) =34360131584a(19) =137439739904a(20) =549757386752