# A052648 (b-file synthesized from sequence entry) 0 0 1 5 2 10 3 30 4 120 5 600 6 3600 7 25200 8 201600 9 1814400 10 18144000 11 199584000 12 2395008000 13 31135104000 14 435891456000 15 6538371840000 16 104613949440000 17 1778437140480000 18 32011868528640000 19 608225502044160000