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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 31 |
| 3 | 416 |
| 4 | 7316 |
| 5 | 158592 |
| 6 | 4079832 |
| 7 | 121418880 |
| 8 | 4102640064 |
| 9 | 155127605760 |
| 10 | 6488944560000 |
| 11 | 297483185986560 |
| 12 | 14831664692912640 |
| 13 | 798949604318423040 |
| 14 | 46240823333993702400 |
| 15 | 2861614126455843225600 |
| 16 | 188557593322666066329600 |
[1,3,31,416,7316,158592,4079832,121418880, 4102640064,155127605760,6488944560000, 297483185986560,14831664692912640, 798949604318423040,46240823333993702400, 2861614126455843225600,188557593322666066329600] |