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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 15 |
| 5 | 42 |
| 6 | 143 |
| 7 | 399 |
| 8 | 1190 |
| 9 | 4209 |
| 10 | 10920 |
| 11 | 37245 |
| 12 | 109886 |
| 13 | 339745 |
| 14 | 1037186 |
| 15 | 3205734 |
| 16 | 9784263 |
| 17 | 29837784 |
| 18 | 93313919 |
| 19 | 289627536 |
[1,2,6,15,42,143,399,1190,4209,10920,37245,109886, 339745,1037186,3205734,9784263,29837784,93313919, 289627536] |