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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 120 |
| 6 | -1800 |
| 7 | 21000 |
| 8 | -235200 |
| 9 | 2693880 |
| 10 | -28690200 |
| 11 | 210447600 |
| 12 | 1465952400 |
| 13 | -123513355680 |
| 14 | 4155643171680 |
| 15 | -114924516470400 |
| 16 | 2886135295680000 |
| 17 | -66750668391381120 |
| 18 | 1375830884058456960 |
| 19 | -22036006671394705920 |
| 20 | 70186623981895296000 |
| 21 | 16180846322732941893120 |
[1,0,0,0,0,120,-1800,21000,-235200,2693880, -28690200,210447600,1465952400,-123513355680, 4155643171680,-114924516470400,2886135295680000, -66750668391381120,1375830884058456960, -22036006671394705920,70186623981895296000, 16180846322732941893120] |