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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 6 |
| 4 | 58 |
| 5 | 702 |
| 6 | 9830 |
| 7 | 152632 |
| 8 | 2565042 |
| 9 | 45938878 |
| 10 | 867667140 |
| 11 | 17154629472 |
| 12 | 353091007048 |
| 13 | 7534733877540 |
| 14 | 166160874412976 |
| 15 | 3777158124019664 |
| 16 | 88326122515058436 |
| 17 | 2121170864722835600 |
| 18 | 52242518805270485716 |
[1,1,6,58,702,9830,152632,2565042,45938878, 867667140,17154629472,353091007048,7534733877540, 166160874412976,3777158124019664, 88326122515058436,2121170864722835600, 52242518805270485716] |