# A002018 (b-file synthesized from sequence entry)
0 1
1 1
2 4
3 33
4 480
5 11010
6 367560
7 16854390
8 1016930880
9 78124095000
10 7446314383200
11 862332613342200
12 119261328828364800
13 19415283189746043600
14 3675162134109650184000
15 800409618620667941886000
16 198730589981586780813696000
17 55800304882692417053710704000