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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 17 |
| 5 | 57 |
| 6 | 533 |
| 7 | 9707 |
| 8 | 296859 |
| 9 | 11801387 |
| 10 | 824137549 |
| 11 | 100677999633 |
| 12 | 19742028440127 |
[1,1,1,17,57,533,9707,296859,11801387,824137549, 100677999633,19742028440127] |