An invertible triangle of ratios of double factorials.

Terms

a(0) =1a(1) =1a(2) =1a(3) =3a(4) =3a(5) =1a(6) =15a(7) =15a(8) =5a(9) =1a(10) =105a(11) =105a(12) =35a(13) =7a(14) =1a(15) =945a(16) =945a(17) =315a(18) =63a(19) =9a(20) =1a(21) =10395a(22) =10395a(23) =3465a(24) =693a(25) =99a(26) =11a(27) =1a(28) =135135a(29) =135135