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

Terms

a(0) =1a(1) =23a(2) =159a(3) =895a(4) =4607a(5) =22527a(6) =106495a(7) =491519a(8) =2228223a(9) =9961471a(10) =44040191a(11) =192937983a(12) =838860799a(13) =3623878655a(14) =15569256447a(15) =66571993087a(16) =283467841535