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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 19 |
| 5 | 62 |
| 6 | 206 |
| 7 | 694 |
| 8 | 2362 |
| 9 | 8101 |
| 10 | 27951 |
| 11 | 96905 |
| 12 | 337298 |
| 13 | 1177935 |
| 14 | 4125287 |
| 15 | 14482481 |
| 16 | 50950871 |
| 17 | 179584544 |
| 18 | 634020055 |
| 19 | 2241695805 |
| 20 | 7936423123 |
| 21 | 28131425351 |
[1,1,2,6,19,62,206,694,2362,8101,27951,96905, 337298,1177935,4125287,14482481,50950871, 179584544,634020055,2241695805,7936423123, 28131425351] |