# A001801 (b-file synthesized from sequence entry)
0 3
1 15
2 105
3 315
4 6930
5 18018
6 90090
7 218790
8 2078505
9 4849845
10 22309287
11 50702925
12 1825305300
13 4071834900
14 18032411700
15 39671305740
16 347123925225
17 755505013725
18 3273855059475
19 7064634602025
20 121511715154830