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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 1 |
| 5 | 6 |
| 6 | 24 |
| 7 | 109 |
| 8 | 477 |
| 9 | 2155 |
| 10 | 9647 |
| 11 | 43621 |
| 12 | 197767 |
| 13 | 901436 |
| 14 | 4125636 |
| 15 | 18964119 |
| 16 | 87508095 |
| 17 | 405289754 |
| 18 | 1883445328 |
| 19 | 8780346115 |
| 20 | 41052409755 |
| 21 | 192461618324 |
| 22 | 904573028990 |
| 23 | 4261485821599 |
| 24 | 20119936936041 |
| 25 | 95186856459869 |
[0,0,0,1,1,6,24,109,477,2155,9647,43621,197767, 901436,4125636,18964119,87508095,405289754, 1883445328,8780346115,41052409755,192461618324, 904573028990,4261485821599,20119936936041, 95186856459869] |