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

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =5a(6) =12a(7) =21a(8) =64a(9) =135a(10) =200a(11) =715a(12) =1368a(13) =455a(14) =4480a(15) =14985a(16) =13440a(17) =111265a(18) =511920a(19) =752115a(20) =425600a(21) =4278015a(22) =1379840a(23) =38386425a(24) =165473280a(25) =35660625a(26) =1921920000a(27) =2430686475a(28) =1614412800a(29) =8228995775