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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 20 |
| 5 | 75 |
| 6 | 294 |
| 7 | 1185 |
| 8 | 4948 |
| 9 | 21134 |
| 10 | 92195 |
| 11 | 408762 |
| 12 | 1835534 |
| 13 | 8332934 |
| 14 | 38172676 |
| 15 | 176241883 |
| 16 | 819216675 |
| 17 | 3830325107 |
| 18 | 18001210955 |
| 19 | 84982319068 |
| 20 | 402802744351 |
| 21 | 1916033752814 |
| 22 | 9143200897213 |
| 23 | 43755960353773 |
| 24 | 209941688871396 |
| 25 | 1009663813004521 |
| 26 | 4866076882958955 |
| 27 | 23497615982212419 |
| 28 | 113668287526782077 |
[1,1,2,6,20,75,294,1185,4948,21134,92195,408762, 1835534,8332934,38172676,176241883,819216675, 3830325107,18001210955,84982319068,402802744351, 1916033752814,9143200897213,43755960353773, 209941688871396,1009663813004521,4866076882958955, 23497615982212419,113668287526782077] |