a(n) = (n+1)*a(n-3), a(0)=a(1)=a(2)=1 for n>1.

Terms

a(0) =1a(1) =1a(2) =1a(3) =4a(4) =5a(5) =6a(6) =28a(7) =40a(8) =54a(9) =280a(10) =440a(11) =648a(12) =3640a(13) =6160a(14) =9720a(15) =58240a(16) =104720a(17) =174960a(18) =1106560a(19) =2094400a(20) =3674160a(21) =24344320a(22) =48171200a(23) =88179840a(24) =608608000a(25) =1252451200a(26) =2380855680a(27) =17041024000a(28) =36321084800a(29) =71425670400