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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 9 |
| 5 | 24 |
| 6 | 175 |
| 7 | 720 |
| 8 | 7665 |
| 9 | 42560 |
| 10 | 436401 |
| 11 | 3628800 |
| 12 | 70215145 |
| 13 | 479001600 |
| 14 | 7116730335 |
| 15 | 88966701824 |
| 16 | 1653438211425 |
| 17 | 20922789888000 |
| 18 | 457688776369825 |
| 19 | 6402373705728000 |
| 20 | 145083396337080201 |
| 21 | 2457732174030848000 |
| 22 | 55735573291977790575 |
| 23 | 1124000727777607680000 |
[1,0,1,2,9,24,175,720,7665,42560,436401,3628800, 70215145,479001600,7116730335,88966701824, 1653438211425,20922789888000,457688776369825, 6402373705728000,145083396337080201, 2457732174030848000,55735573291977790575, 1124000727777607680000] |