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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 6 |
| 3 | 54 |
| 4 | 780 |
| 5 | 16500 |
| 6 | 465240 |
| 7 | 16486512 |
| 8 | 708621480 |
| 9 | 36072738648 |
| 10 | 2137167558432 |
| 11 | 145394086979328 |
| 12 | 11236518532643184 |
| 13 | 977782595316947472 |
| 14 | 95086323023335926048 |
| 15 | 10266902547496839586848 |
| 16 | 1223846872961573356310112 |
[1,3,6,54,780,16500,465240,16486512,708621480, 36072738648,2137167558432,145394086979328, 11236518532643184,977782595316947472, 95086323023335926048,10266902547496839586848, 1223846872961573356310112] |