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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 18 |
| 2 | 1050 |
| 3 | 77616 |
| 4 | 6370650 |
| 5 | 554822268 |
| 6 | 50199951984 |
| 7 | 4664758248000 |
| 8 | 442077195513690 |
| 9 | 42533571002422500 |
| 10 | 4141601026094832300 |
| 11 | 407220411993767798400 |
| 12 | 40363606408574136870000 |
| 13 | 4028061310168832261158176 |
| 14 | 404311537318239680601595200 |
| 15 | 40785601782042745410592271616 |
[1,18,1050,77616,6370650,554822268,50199951984, 4664758248000,442077195513690,42533571002422500, 4141601026094832300,407220411993767798400, 40363606408574136870000,4028061310168832261158176, 404311537318239680601595200, 40785601782042745410592271616] |