a(n) = 2^(n-1)*(9*n-16) + 9.

Terms

a(0) =1a(1) =2a(2) =13a(3) =53a(4) =169a(5) =473a(6) =1225a(7) =3017a(8) =7177a(9) =16649a(10) =37897a(11) =85001a(12) =188425a(13) =413705a(14) =901129a(15) =1949705a(16) =4194313a(17) =8978441a(18) =19136521a(19) =40632329a(20) =85983241a(21) =181403657a(22) =381681673a(23) =801112073a(24) =1677721609a(25) =3506438153a(26) =7314866185a(27) =15233712137a(28) =31675383817a(29) =65766686729