# A005562 (b-file synthesized from sequence entry)
4 1
5 5
6 35
7 140
8 720
9 2700
10 12375
11 45375
12 196625
13 715715
14 3006003
15 10930920
16 45048640
17 164105760
18 668144880
19 2441298600
20 9859090500
21 36149998500