a(n) = A091137(n)/2^n.

Terms

a(0) =1a(1) =1a(2) =3a(3) =3a(4) =45a(5) =45a(6) =945a(7) =945a(8) =14175a(9) =14175a(10) =467775a(11) =467775a(12) =638512875a(13) =638512875a(14) =1915538625a(15) =1915538625a(16) =488462349375a(17) =488462349375