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| n | a(n) |
|---|---|
| 2 | 2 |
| 3 | 2 |
| 4 | 7 |
| 5 | 7 |
| 6 | 21 |
| 7 | 42 |
| 8 | 71 |
| 9 | 268 |
| 10 | 611 |
| 11 | 1352 |
| 12 | 3099 |
| 13 | 8471 |
| 14 | 23877 |
| 15 | 63564 |
| 16 | 182771 |
| 17 | 527001 |
| 18 | 1671752 |
| 19 | 5055853 |
[2,2,7,7,21,42,71,268,611,1352,3099,8471,23877, 63564,182771,527001,1671752,5055853] |