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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 6 |
| 4 | 15 |
| 5 | 21 |
| 6 | 24 |
| 7 | 31 |
| 8 | 291 |
| 9 | 408 |
| 10 | 457 |
| 11 | 643 |
| 12 | 2671 |
| 13 | 2676 |
| 14 | 10893 |
| 15 | 21151 |
| 16 | 26445 |
| 17 | 77304 |
| 18 | 96312 |
[1,3,6,15,21,24,31,291,408,457,643,2671,2676, 10893,21151,26445,77304,96312] |