# A003584 (b-file synthesized from sequence entry)
0 1
1 2
2 9
3 52
4 336
5 2304
6 16368
7 118976
8 878592
9 6562816
10 49447424
11 375072768
12 2860343296
13 21909012480
14 168425533440
15 1298753372160
16 10041201131520
17 77809145610240
18 604138825973760
19 4698956908462080
20 36604934482821120