# A143648 (b-file synthesized from sequence entry)
0 1
1 4
2 22
3 136
4 868
5 5584
6 35992
7 232096
8 1496848
9 9653824
10 62262112
11 401558656
12 2589848128
13 16703198464
14 107727106432
15 694784866816
16 4481007870208
17 28900214293504
18 186391635645952
19 1202130942232576
20 7753131181401088