# A122394 (b-file synthesized from sequence entry)
0 1
1 4
2 19
3 95
4 475
5 2376
6 11881
7 59406
8 297029
9 1485144
10 7425719
11 37128595
12 185642975
13 928214876
14 4641074381
15 23205371904
16 116026859520
17 580134297600
18 2900671488000
19 14503357440000
20 72516787200000
21 362583936000000