# A307642 (b-file synthesized from sequence entry)
1 1
2 8
3 57
4 428
5 3510
6 31644
7 312984
8 3380544
9 39664080
10 502927200
11 6858181440
12 100135491840
13 1559197261440
14 25797280723200
15 452046655872000
16 8364495012249600
17 162994310248089600
18 3336683369519001600
19 71596721810396160000
20 1606993396943155200000