# A144888 (b-file synthesized from sequence entry)
0 1
1 4
2 36
3 200
4 1720
5 12480
6 118560
7 1081920
8 11793600
9 131443200
10 1658764800
11 21990528000
12 319711795200
13 4922394624000
14 81508654080000
15 1428114530304000
16 26582538673152000
17 521466739605504000
18 10779099461222400000
19 233753593186713600000
20 5310546788872765440000