# A221988 (b-file synthesized from sequence entry)
0 1
1 2
2 6
3 24
4 116
5 664
6 4392
7 32928
8 276016
9 2557856
10 25965408
11 286538112
12 3415359296
13 43727878528
14 598510015104
15 8720853182976
16 134778021389056
17 2202055694727680
18 37923940767905280
19 686639853639505920
20 13038833241899856896
21 259119925532534413312