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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 5 |
| 4 | 15 |
| 5 | 52 |
| 6 | 187 |
| 7 | 677 |
| 8 | 2439 |
| 9 | 8707 |
| 10 | 30871 |
| 11 | 108696 |
| 12 | 380653 |
| 13 | 1328193 |
| 14 | 4623194 |
| 15 | 16065161 |
| 16 | 55763738 |
| 17 | 193430602 |
| 18 | 670683122 |
| 19 | 2324853720 |
| 20 | 8057594663 |
| 21 | 27923827498 |
| 22 | 96765523944 |
| 23 | 335314355594 |
| 24 | 1161917842116 |
| 25 | 4026187435945 |
| 26 | 13951144657754 |
| 27 | 48341945365173 |
[1,1,2,5,15,52,187,677,2439,8707,30871,108696, 380653,1328193,4623194,16065161,55763738, 193430602,670683122,2324853720,8057594663, 27923827498,96765523944,335314355594, 1161917842116,4026187435945,13951144657754, 48341945365173] |