# A109923 (b-file synthesized from sequence entry)
2 1
3 4
4 15
5 420
6 3960
7 80080
8 1225224
9 19399380
10 5354228880
11 145568097675
12 7600186994400
13 254425307479200
14 9957281351799600
15 392482839950100900
16 114779426083185063200
17 5474978624167927514640
18 312603618218620377448800