# A113247 (b-file synthesized from sequence entry)
0 1
1 1
2 2
3 4
4 16
5 64
6 384
7 2544
8 20352
9 181632
10 1816320
11 19960320
12 239523840
13 3113533440
14 43589468160
15 653837506560
16 10461400104960
17 177843719208960
18 3201186945761280
19 60822550297313280
20 1216451005946265600