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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 21 |
| 5 | 74 |
| 6 | 256 |
| 7 | 880 |
| 8 | 3025 |
| 9 | 10406 |
| 10 | 35805 |
| 11 | 123197 |
| 12 | 423881 |
| 13 | 1458425 |
| 14 | 5017929 |
| 15 | 17264954 |
| 16 | 59402739 |
| 17 | 204384285 |
| 18 | 703215622 |
| 19 | 2419521666 |
| 20 | 8324736993 |
| 21 | 28642540011 |
| 22 | 98549071193 |
| 23 | 339073260558 |
| 24 | 1166633785846 |
| 25 | 4013983255478 |
[1,2,6,21,74,256,880,3025,10406,35805,123197, 423881,1458425,5017929,17264954,59402739, 204384285,703215622,2419521666,8324736993, 28642540011,98549071193,339073260558, 1166633785846,4013983255478] |