# A121355 (b-file synthesized from sequence entry)
1 1
2 1
3 8
4 48
5 120
6 2640
7 30240
8 201600
9 4838400
10 96163200
11 1037836800
12 30496435200
13 828193766400
14 13686991718400
15 450537408921600
16 15880397524992000
17 356398802952192000
18 13410127414075392000
19 569542360114151424000
20 16614774394239909888000