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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 12 |
| 3 | 540 |
| 4 | 21000 |
| 5 | 785820 |
| 6 | 28956312 |
| 7 | 1058809752 |
| 8 | 38545567632 |
| 9 | 1399354322652 |
| 10 | 50707958458872 |
| 11 | 1835099465988360 |
| 12 | 66348521294296176 |
| 13 | 2397139928161319640 |
| 14 | 86559958069097395440 |
| 15 | 3124302168622853150640 |
| 16 | 112729791393354644416800 |
[0,12,540,21000,785820,28956312,1058809752, 38545567632,1399354322652,50707958458872, 1835099465988360,66348521294296176, 2397139928161319640,86559958069097395440, 3124302168622853150640,112729791393354644416800] |