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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 2 |
| 5 | 4 |
| 6 | 10 |
| 7 | 20 |
| 8 | 44 |
| 9 | 93 |
| 10 | 198 |
| 11 | 414 |
| 12 | 864 |
| 13 | 1788 |
| 14 | 3687 |
| 15 | 7541 |
| 16 | 15382 |
| 17 | 31200 |
| 18 | 63191 |
| 19 | 127482 |
| 20 | 256857 |
| 21 | 516404 |
| 22 | 1037104 |
| 23 | 2080357 |
| 24 | 4170283 |
| 25 | 8354078 |
| 26 | 16728270 |
[0,0,1,2,4,10,20,44,93,198,414,864,1788,3687,7541, 15382,31200,63191,127482,256857,516404,1037104, 2080357,4170283,8354078,16728270] |