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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 6 |
| 4 | 21 |
| 5 | 120 |
| 6 | 765 |
| 7 | 5376 |
| 8 | 46473 |
| 9 | 415104 |
| 10 | 4371225 |
| 11 | 48143744 |
| 12 | 594635613 |
| 13 | 7784817664 |
| 14 | 110691178325 |
| 15 | 1673986906112 |
| 16 | 27018807872657 |
| 17 | 462531126525952 |
| 18 | 8370279766396593 |
| 19 | 159859054841331712 |
[1,1,1,6,21,120,765,5376,46473,415104,4371225, 48143744,594635613,7784817664,110691178325, 1673986906112,27018807872657,462531126525952, 8370279766396593,159859054841331712] |