a(n) = !n mod n!!.

Terms

a(0) =0a(1) =0a(2) =1a(3) =2a(4) =1a(5) =14a(6) =25a(7) =69a(8) =241a(9) =251a(10) =2481a(11) =6830a(12) =4921a(13) =119547a(14) =250489a(15) =780584a(16) =8507745a(17) =5562314a(18) =2246113a(19) =592853256a(20) =853522921a(21) =1510777190a(22) =67329163881a(23) =131984971712a(25) =132447220974