# A293487 (b-file synthesized from sequence entry) 0 1 1 1 2 0 3 6 4 24 5 120 6 720 7 5040 8 80640 9 725760 10 7257600 11 79833600 12 1437004800 13 18681062400 14 261534873600 15 5230697472000 16 104613949440000 17 1778437140480000 18 32011868528640000 19 729870602452992000 20 17030314057236480000 21 408727537373675520000 22 8992005822220861440000