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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 1 |
| 5 | 9 |
| 6 | 49 |
| 7 | 281 |
| 8 | 1345 |
| 9 | 13233 |
| 10 | 105441 |
| 11 | 1179729 |
| 12 | 10336833 |
| 13 | 144386553 |
| 14 | 1580651409 |
| 15 | 25501409961 |
| 16 | 316289380737 |
| 17 | 5869292202465 |
| 18 | 83559601907649 |
| 19 | 1744083324947745 |
| 20 | 27709107620492673 |
| 21 | 643531258862953065 |
[1,1,1,1,1,9,49,281,1345,13233,105441,1179729, 10336833,144386553,1580651409,25501409961, 316289380737,5869292202465,83559601907649, 1744083324947745,27709107620492673, 643531258862953065] |