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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 16 |
| 5 | 126 |
| 6 | 1333 |
| 7 | 17895 |
| 8 | 293461 |
| 9 | 5721390 |
| 10 | 129948787 |
| 11 | 3384796695 |
| 12 | 99848190706 |
| 13 | 3301868304168 |
| 14 | 121369298328835 |
| 15 | 4923587573624940 |
| 16 | 219090125559917698 |
| 17 | 10637377855875861600 |
| 18 | 560928617456424367993 |
| 19 | 31993928581562975604588 |
| 20 | 1966682218962058310721178 |
[1,1,3,16,126,1333,17895,293461,5721390,129948787, 3384796695,99848190706,3301868304168, 121369298328835,4923587573624940, 219090125559917698,10637377855875861600, 560928617456424367993,31993928581562975604588, 1966682218962058310721178] |