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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 7 |
| 3 | 31 |
| 4 | 187 |
| 5 | 990 |
| 6 | 5721 |
| 7 | 32155 |
| 8 | 185667 |
| 9 | 1068413 |
| 10 | 6209614 |
| 11 | 36152732 |
| 12 | 211488161 |
| 13 | 1240108650 |
| 14 | 7292753853 |
| 15 | 42976317875 |
| 16 | 253780411459 |
| 17 | 1501160467318 |
| 18 | 8893657851979 |
| 19 | 52763660745169 |
| 20 | 313428125418614 |
| 21 | 1863953435747000 |
[1,7,31,187,990,5721,32155,185667,1068413,6209614, 36152732,211488161,1240108650,7292753853, 42976317875,253780411459,1501160467318, 8893657851979,52763660745169,313428125418614, 1863953435747000] |