# A004387 (b-file synthesized from sequence entry)
6 1
7 56
8 2016
9 59640
10 1581580
11 39175752
12 927048304
13 21243342120
14 475491062970
15 10456592670160
16 226846154180800
17 4868956823342976
18 103619293824707388
19 2190038132512694800
20 46026828991565696400