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

Terms

a(0) =1a(1) =2a(2) =6a(3) =18a(4) =50a(5) =130a(6) =322a(7) =770a(8) =1794a(9) =4098a(10) =9218a(11) =20482a(12) =45058a(13) =98306a(14) =212994a(15) =458754a(16) =983042a(17) =2097154a(18) =4456450a(19) =9437186a(20) =19922946a(21) =41943042a(22) =88080386a(23) =184549378a(24) =385875970a(25) =805306370a(26) =1677721602a(27) =3489660930a(28) =7247757314a(29) =15032385538