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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 8 |
| 4 | 48 |
| 5 | 286 |
| 6 | 1748 |
| 7 | 10734 |
| 8 | 65934 |
| 9 | 404984 |
| 10 | 2487534 |
| 11 | 15279170 |
| 12 | 93849326 |
| 13 | 576451382 |
| 14 | 3540741892 |
| 15 | 21748327444 |
| 16 | 133584927368 |
| 17 | 820519778376 |
| 18 | 5039885260498 |
| 19 | 30956527928058 |
| 20 | 190144531428150 |
| 21 | 1167926290556226 |
[0,0,8,48,286,1748,10734,65934,404984,2487534, 15279170,93849326,576451382,3540741892, 21748327444,133584927368,820519778376, 5039885260498,30956527928058,190144531428150, 1167926290556226] |