# A073980 (b-file synthesized from sequence entry)
1 0
2 0
3 3
4 36
5 300
6 1620
7 8100
8 44928
9 262440
10 1574640
11 9722592
12 60466176
13 369476640
14 2213827200
15 13162730688
16 78364164096
17 468419708160
18 2810089946880
19 16891882995456
20 101554796888064
21 609954817881600
22 3659728907289600
23 21947538146863104
24 131621703842267136