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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 2 |
| 3 | 6 |
| 4 | 36 |
| 5 | 360 |
| 6 | 3000 |
| 7 | 40320 |
| 8 | 532560 |
| 9 | 8527680 |
| 10 | 152591040 |
| 11 | 2987107200 |
| 12 | 65408333760 |
| 13 | 1544664401280 |
| 14 | 39767121313920 |
| 15 | 1100734899264000 |
| 16 | 32661264290054400 |
| 17 | 1034874195222067200 |
| 18 | 34834463447361177600 |
| 19 | 1242657968679512985600 |
| 20 | 46804841790705090892800 |
[1,0,2,6,36,360,3000,40320,532560,8527680, 152591040,2987107200,65408333760,1544664401280, 39767121313920,1100734899264000,32661264290054400, 1034874195222067200,34834463447361177600, 1242657968679512985600,46804841790705090892800] |