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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 10 |
| 5 | 28 |
| 6 | 85 |
| 7 | 253 |
| 8 | 784 |
| 9 | 2461 |
| 10 | 7813 |
| 11 | 25138 |
| 12 | 81571 |
| 13 | 266905 |
| 14 | 879607 |
| 15 | 2916490 |
| 16 | 9723574 |
| 17 | 32575906 |
| 18 | 109610770 |
| 19 | 370264726 |
| 20 | 1255188745 |
| 21 | 4268794369 |
| 22 | 14560608043 |
| 23 | 49799556244 |
| 24 | 170745718477 |
| 25 | 586772531173 |
| 26 | 2020746285703 |
| 27 | 6972847835854 |
| 28 | 24104939909734 |
| 29 | 83473064245378 |
[1,1,1,4,10,28,85,253,784,2461,7813,25138,81571, 266905,879607,2916490,9723574,32575906,109610770, 370264726,1255188745,4268794369,14560608043, 49799556244,170745718477,586772531173, 2020746285703,6972847835854,24104939909734, 83473064245378] |