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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 3 |
| 5 | 7 |
| 6 | 19 |
| 7 | 50 |
| 8 | 129 |
| 9 | 334 |
| 10 | 862 |
| 11 | 2220 |
| 12 | 5715 |
| 13 | 14706 |
| 14 | 37836 |
| 15 | 97353 |
| 16 | 250535 |
| 17 | 644905 |
| 18 | 1660558 |
| 19 | 4277165 |
| 20 | 11020698 |
| 21 | 28406449 |
| 22 | 73245390 |
| 23 | 188928736 |
| 24 | 487492213 |
| 25 | 1258305122 |
| 26 | 3248994414 |
| 27 | 8391747865 |
| 28 | 21681628237 |
| 29 | 56035444491 |
| 30 | 144864062529 |
[0,0,0,1,3,7,19,50,129,334,862,2220,5715,14706, 37836,97353,250535,644905,1660558,4277165, 11020698,28406449,73245390,188928736,487492213, 1258305122,3248994414,8391747865,21681628237, 56035444491,144864062529] |