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

Terms

a(0) =1a(1) =9a(2) =35a(3) =105a(4) =279a(5) =693a(6) =1651a(7) =3825a(8) =8687a(9) =19437a(10) =42987a(11) =94185a(12) =204775a(13) =442341a(14) =950243a(15) =2031585a(16) =4325343a(17) =9175005a(18) =19398619a(19) =40894425a(20) =85983191a(21) =180355029a(22) =377487315a(23) =788529105a(24) =1644167119a(25) =3422552013a(26) =7113539531a(27) =14763950025a(28) =30601641927a(29) =63350767557