# A226968 (b-file synthesized from sequence entry)
0 0
1 1
2 1
3 8
4 30
5 264
6 1920
7 20880
8 226800
9 3064320
10 43908480
11 722131200
12 12773376000
13 249559833600
14 5236924492800
15 118911189196800
16 2883421981440000
17 74715282690048000
18 2054450584682496000
19 59855791774851072000
20 1839882143683584000000