# A007727 (b-file synthesized from sequence entry)
0 1
1 2
2 4
3 18
4 64
5 250
6 900
7 3430
8 12800
9 48600
10 184500
11 705430
12 2703168
13 10400598
14 40113164
15 155117250
16 601067520
17 2333606218
18 9075085776
19 35345263798
20 137846344000
21 538257870990
22 2104098258284
23 8233430727598
24 32247600966144