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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 28 |
| 4 | 1668 |
| 5 | 29092 |
| 6 | 252584 |
| 7 | 1441634 |
| 8 | 6222996 |
| 9 | 22004086 |
| 10 | 66972760 |
| 11 | 181332416 |
| 12 | 446905476 |
| 13 | 1019470032 |
| 14 | 2179712872 |
| 15 | 4410518630 |
| 16 | 8510498516 |
| 17 | 15756224370 |
| 18 | 28128603736 |
| 19 | 48622240660 |
| 20 | 81660504068 |
| 21 | 133643402268 |
| 22 | 213660267432 |
[0,0,28,1668,29092,252584,1441634,6222996, 22004086,66972760,181332416,446905476,1019470032, 2179712872,4410518630,8510498516,15756224370, 28128603736,48622240660,81660504068,133643402268, 213660267432] |