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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 10 |
| 5 | 20 |
| 6 | 56 |
| 7 | 116 |
| 8 | 320 |
| 9 | 736 |
| 10 | 1872 |
| 11 | 4176 |
| 12 | 12712 |
| 13 | 28368 |
| 14 | 73592 |
| 15 | 177272 |
| 16 | 487304 |
| 17 | 1130712 |
| 18 | 3209792 |
| 19 | 7494720 |
| 20 | 20419744 |
| 21 | 49706280 |
| 22 | 129803592 |
| 23 | 311179624 |
[1,1,2,4,10,20,56,116,320,736,1872,4176,12712, 28368,73592,177272,487304,1130712,3209792,7494720, 20419744,49706280,129803592,311179624] |