Union of the factorial numbers (A000142) and the double factorials numbers (A006882).

Terms

a(0) =1a(1) =2a(2) =3a(3) =6a(4) =8a(5) =15a(6) =24a(7) =48a(8) =105a(9) =120a(10) =384a(11) =720a(12) =945a(13) =3840a(14) =5040a(15) =10395a(16) =40320a(17) =46080a(18) =135135a(19) =362880a(20) =645120a(21) =2027025a(22) =3628800a(23) =10321920a(24) =34459425a(25) =39916800a(26) =185794560a(27) =479001600a(28) =654729075a(29) =3715891200