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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 18 |
| 2 | 245 |
| 3 | 3135 |
| 4 | 40369 |
| 5 | 537628 |
| 6 | 7494416 |
| 7 | 109911300 |
| 8 | 1698920916 |
| 9 | 27679825272 |
| 10 | 474957547272 |
| 11 | 8572072384512 |
| 12 | 162478082312064 |
| 13 | 3229079010579072 |
| 14 | 67177961946534528 |
| 15 | 1460629706845766400 |
| 16 | 33139181950164806400 |
| 17 | 783398920650352012800 |
| 18 | 19268391564147377318400 |
[1,18,245,3135,40369,537628,7494416,109911300, 1698920916,27679825272,474957547272,8572072384512, 162478082312064,3229079010579072, 67177961946534528,1460629706845766400, 33139181950164806400,783398920650352012800, 19268391564147377318400] |