# A055533 (b-file synthesized from sequence entry)
2 1
3 12
4 108
5 960
6 9000
7 90720
8 987840
9 11612160
10 146966400
11 1995840000
12 28979596800
13 448345497600
14 7366565606400
15 128152088064000
16 2353813862400000
17 45527990796288000
18 925143000477696000