# A281024 (b-file synthesized from sequence entry)
1 1
2 2
3 6
4 36
5 180
6 2700
7 18900
8 378000
9 6804000
10 238140000
11 2619540000
12 141455160000
13 1838917080000
14 115851776040000
15 6951106562400000
16 500479672492800000
17 8508154432377600000
18 995454068588179200000
19 18913627303175404800000
20 2458771549412802624000000