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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 20 |
| 5 | 76 |
| 6 | 269 |
| 7 | 979 |
| 8 | 3552 |
| 9 | 13068 |
| 10 | 47999 |
| 11 | 177283 |
| 12 | 655064 |
| 13 | 2425417 |
| 14 | 8986341 |
| 15 | 33341753 |
| 16 | 123816292 |
| 17 | 460226315 |
| 18 | 1711870476 |
| 19 | 6371885563 |
| 20 | 23731057146 |
| 21 | 88430326347 |
| 22 | 329681018798 |
| 23 | 1229642693864 |
| 24 | 4588155649388 |
| 25 | 17126079485326 |
[1,2,6,20,76,269,979,3552,13068,47999,177283, 655064,2425417,8986341,33341753,123816292, 460226315,1711870476,6371885563,23731057146, 88430326347,329681018798,1229642693864, 4588155649388,17126079485326] |