n | a(n) |
---|---|
0 | -1 |
1 | 1 |
2 | 0 |
3 | 2 |
4 | 2 |
5 | 10 |
6 | 20 |
7 | 80 |
8 | 220 |
9 | 860 |
10 | 2840 |
11 | 11440 |
12 | 42680 |
13 | 179960 |
14 | 734800 |
15 | 3254240 |
16 | 14276240 |
17 | 66344080 |
18 | 309040160 |
19 | 1503233600 |
20 | 7374996640 |
21 | 37439668640 |
22 | 192314598080 |
23 | 1015987308160 |
24 | 5439223064000 |
25 | 29822918459840 |
26 | 165803495059840 |
27 | 941199375015680 |
[-1,1,0,2,2,10,20,80,220,860,2840,11440,42680, 179960,734800,3254240,14276240,66344080,309040160, 1503233600,7374996640,37439668640,192314598080, 1015987308160,5439223064000,29822918459840, 165803495059840,941199375015680] |