# A006974 (b-file synthesized from sequence entry)
0 1
1 9
2 50
3 220
4 840
5 2912
6 9408
7 28800
8 84480
9 239360
10 658944
11 1770496
12 4659200
13 12042240
14 30638080
15 76873728
16 190513152
17 466944000
18 1133117440
19 2724986880
20 6499598336
21 15386804224
22 36175872000
23 84515225600
24 196293427200
25 453437816832