Partial products of A006257.

Terms

a(0) =1a(1) =1a(2) =3a(3) =3a(4) =9a(5) =45a(6) =315a(7) =315a(8) =945a(9) =4725a(10) =33075a(11) =297675a(12) =3274425a(13) =42567525a(14) =638512875a(15) =638512875a(16) =1915538625a(17) =9577693125a(18) =67043851875a(19) =603394666875