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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 6 |
| 3 | 64 |
| 4 | 1020 |
| 5 | 21854 |
| 6 | 590248 |
| 7 | 19268098 |
| 8 | 738194780 |
| 9 | 32481348812 |
| 10 | 1614506203400 |
| 11 | 89478362311442 |
| 12 | 5471239864890436 |
| 13 | 365900668319641264 |
| 14 | 26569358218427144576 |
| 15 | 2081825562568924254126 |
| 16 | 175078869470374599592604 |
| 17 | 15730138729512408087404292 |
[1,1,6,64,1020,21854,590248,19268098,738194780, 32481348812,1614506203400,89478362311442, 5471239864890436,365900668319641264, 26569358218427144576,2081825562568924254126, 175078869470374599592604, 15730138729512408087404292] |