# A319948 (b-file synthesized from sequence entry) 1 1 2 3 3 12 4 72 5 504 6 4536 7 45360 8 544320 9 7076160 10 106142400 11 1698278400 12 30569011200 13 580811212800 14 12197035468800 15 268334780313600 16 6440034727526400 17 161000868188160000 18 4347023441080320000 19 121716656350248960000 20 3651499690507468800000