# A144895 (b-file synthesized from sequence entry)
0 1
1 2
2 10
3 36
4 204
5 1104
6 7776
7 57600
8 505440
9 4803840
10 51442560
11 597784320
12 7609593600
13 104364288000
14 1541746483200
15 24329797632000
16 409042632499200
17 7290954768384000
18 137384159367168000
19 2727604332085248000
20 56913717580296192000
21 1244955414746824704000