# A155456 (b-file synthesized from sequence entry)
0 -1
1 -1
2 1
3 -2
4 6
5 -24
6 120
7 -720
8 5040
9 -40320
10 362880
11 -3628800
12 39916800
13 -479001600
14 6227020800
15 -87178291200
16 1307674368000
17 -20922789888000
18 355687428096000
19 -6402373705728000
20 121645100408832000