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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 13 |
| 3 | 169 |
| 4 | 1040 |
| 5 | 6400 |
| 6 | 53280 |
| 7 | 443556 |
| 8 | 3383280 |
| 9 | 25806400 |
| 10 | 203738480 |
| 11 | 1608491236 |
| 12 | 12558632416 |
| 13 | 98054154496 |
| 14 | 768752950768 |
| 15 | 6027088830169 |
| 16 | 47188038099235 |
| 17 | 369450492999025 |
| 18 | 2893968831142495 |
| 19 | 22668952280018641 |
| 20 | 177540636808778880 |
[1,13,169,1040,6400,53280,443556,3383280,25806400, 203738480,1608491236,12558632416,98054154496, 768752950768,6027088830169,47188038099235, 369450492999025,2893968831142495, 22668952280018641,177540636808778880] |