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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 25 |
| 5 | 366 |
| 6 | 5491 |
| 7 | 176569 |
| 8 | 5332097 |
| 9 | 276268942 |
| 10 | 13470365431 |
| 11 | 1135683784753 |
| 12 | 75066413338423 |
| 13 | 9256260956838520 |
| 14 | 918768523598548169 |
| 15 | 140268128758724744770 |
| 16 | 18398287904991375995745 |
| 17 | 3879391299475140314514162 |
| 18 | 594721341754741064012714341 |
[1,1,4,25,366,5491,176569,5332097,276268942, 13470365431,1135683784753,75066413338423, 9256260956838520,918768523598548169, 140268128758724744770,18398287904991375995745, 3879391299475140314514162, 594721341754741064012714341] |