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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 4 |
| 5 | 3 |
| 6 | 13 |
| 7 | 43 |
| 8 | 580 |
| 9 | 1897 |
| 10 | 23851 |
| 11 | 149041 |
| 12 | 14348161 |
| 13 | 74552521 |
| 14 | 7849966951 |
| 15 | 311500453881 |
| 16 | 64690704744716 |
| 17 | 2466747100788601 |
| 18 | 493809829542170401 |
[1,1,1,4,3,13,43,580,1897,23851,149041,14348161, 74552521,7849966951,311500453881,64690704744716, 2466747100788601,493809829542170401] |