# A012251 (b-file synthesized from sequence entry)
0 1
1 1
2 1
3 -2
4 -11
5 24
6 349
7 -720
8 -22455
9 40320
10 2465241
11 -3628800
12 -416217603
13 479001600
14 100729124469
15 -87178291200
16 -33198564667887
17 20922789888000
18 14328891118054449
19 -6402373705728000
20 -7852649782447649403