4th-order non-linear ("factorial") recursion: a(0)=a(1)=a(2)=a(3)=1, a(n) = (n+1)*a(n-4).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =5a(5) =6a(6) =7a(7) =8a(8) =45a(9) =60a(10) =77a(11) =96a(12) =585a(13) =840a(14) =1155a(15) =1536a(16) =9945a(17) =15120a(18) =21945a(19) =30720a(20) =208845a(21) =332640a(22) =504735a(23) =737280a(24) =5221125a(25) =8648640a(26) =13627845a(27) =20643840a(28) =151412625a(29) =259459200