a(n) = A293564(n) - 1.

Terms

a(0) =1a(1) =2a(2) =6a(3) =26a(4) =40a(5) =94a(6) =184a(7) =350a(8) =496a(9) =3390a(10) =3536a(11) =45370a(12) =82734a(13) =99064a(14) =357164a(15) =840904a(16) =3880556a(17) =27914936a(18) =40517520a(19) =104715206a(20) =1126506904a(21) =2084910530a(22) =2442825346a(23) =4332318176a(24) =6716598046a(25) =17736392220a(26) =18205380336a(27) =30869303806a(28) =68506021364a(29) =78491213264