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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 1 |
| 5 | 1 |
| 6 | 7 |
| 7 | 21 |
| 8 | 51 |
| 9 | 261 |
| 10 | 1539 |
| 11 | 11759 |
| 12 | 111585 |
| 13 | 1296125 |
| 14 | 18399415 |
| 15 | 335874781 |
| 16 | 7824897067 |
| 17 | 229077144211 |
| 18 | 8419643660275 |
| 19 | 387472393043501 |
| 20 | 22360944601180667 |
[1,1,1,1,1,7,21,51,261,1539,11759,111585,1296125, 18399415,335874781,7824897067,229077144211, 8419643660275,387472393043501,22360944601180667] |