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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 6 |
| 5 | 18 |
| 6 | 32 |
| 7 | 85 |
| 8 | 165 |
| 9 | 411 |
| 10 | 839 |
| 11 | 2013 |
| 12 | 4237 |
| 13 | 9933 |
| 14 | 21317 |
| 15 | 49236 |
| 16 | 107014 |
| 17 | 244750 |
| 18 | 536500 |
| 19 | 1218888 |
| 20 | 2687362 |
| 21 | 6077644 |
| 22 | 13453606 |
| 23 | 30329434 |
| 24 | 67326816 |
| 25 | 151439158 |
| 26 | 336842092 |
| 27 | 756452890 |
| 28 | 1684953360 |
| 29 | 3779590010 |
| 30 | 8427441240 |
[0,1,1,4,6,18,32,85,165,411,839,2013,4237,9933, 21317,49236,107014,244750,536500,1218888,2687362, 6077644,13453606,30329434,67326816,151439158, 336842092,756452890,1684953360,3779590010, 8427441240] |