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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 9 |
| 2 | 72 |
| 3 | 720 |
| 4 | 6480 |
| 5 | 59040 |
| 6 | 530640 |
| 7 | 4782960 |
| 8 | 43040160 |
| 9 | 387419760 |
| 10 | 3486725280 |
| 11 | 31381059600 |
| 12 | 282428998560 |
| 13 | 2541865828320 |
| 14 | 22876787671920 |
| 15 | 205891132034880 |
| 16 | 1853020145805120 |
| 17 | 16677181699666560 |
| 18 | 150094634909047920 |
| 19 | 1350851717672992080 |
| 20 | 12157665455570137920 |
[1,9,72,720,6480,59040,530640,4782960,43040160, 387419760,3486725280,31381059600,282428998560, 2541865828320,22876787671920,205891132034880, 1853020145805120,16677181699666560, 150094634909047920,1350851717672992080, 12157665455570137920] |