# A012254 (b-file synthesized from sequence entry)
0 1
1 1
2 1
3 2
4 5
5 24
6 109
7 720
8 4521
9 40320
10 330681
11 3628800
12 36468717
13 479001600
14 5721101541
15 87178291200
16 1205289090513
17 20922789888000
18 328897528901361
19 6402373705728000
20 112769846051251797
21 2432902008176640000