# A013140 (b-file synthesized from sequence entry)
0 1
1 2
2 4
3 4
4 -16
5 -88
6 64
7 2496
8 4096
9 -106624
10 -480896
11 6875136
12 54717440
13 -673392640
14 -7775895552
15 99550288896
16 1454255472640
17 -21279326830592
18 -360442602684416
19 6159283224084480
20 116460747215831040