Quadruple factorial numbers n!!!!: a(n) = n*a(n-4).

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =4a(5) =5a(6) =12a(7) =21a(8) =32a(9) =45a(10) =120a(11) =231a(12) =384a(13) =585a(14) =1680a(15) =3465a(16) =6144a(17) =9945a(18) =30240a(19) =65835a(20) =122880a(21) =208845a(22) =665280a(23) =1514205a(24) =2949120a(25) =5221125a(26) =17297280a(27) =40883535a(28) =82575360a(29) =151412625