# A005921 (b-file synthesized from sequence entry)
0 1
1 3
2 10
3 48
4 312
5 2520
6 24480
7 277200
8 3588480
9 52254720
10 845510400
11 15048633600
12 292190976000
13 6146069529600
14 139223731046400
15 3379030566912000
16 87478184521728000
17 2406225451069440000
18 70080382582898688000