# A201720 (b-file synthesized from sequence entry)
0 0
1 1
2 3
3 12
4 64
5 420
6 3246
7 28798
8 288072
9 3205044
10 39234340
11 523821936
12 7572221328
13 117792884872
14 1961516974704
15 34807390821960
16 655594811020096
17 13060711726818768
18 274358217793164912
19 6060159633360214144
20 140404595387426964480