# A181964 (b-file synthesized from sequence entry)
1 1
2 1
3 6
4 36
5 240
6 2160
7 20160
8 241920
9 2903040
10 39916800
11 578793600
12 9580032000
13 161902540800
14 3007651046400
15 58845346560000
16 1234444603392000
17 26854400821248000
18 624231436308480000
19 15083992450695168000
20 385614968295997440000