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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 2 |
| 5 | 16 |
| 6 | 93 |
| 7 | 503 |
| 8 | 2736 |
| 9 | 15397 |
| 10 | 90556 |
| 11 | 558245 |
| 12 | 3607387 |
| 13 | 24409819 |
| 14 | 172696471 |
| 15 | 1275310652 |
| 16 | 9813238958 |
| 17 | 78548445033 |
| 18 | 652960116962 |
| 19 | 5628482431333 |
| 20 | 50236822145840 |
| 21 | 463647958566143 |
| 22 | 4419123858908203 |
| 23 | 43445718995990792 |
| 24 | 440083379418080388 |
| 25 | 4588225614805060248 |
[0,0,0,0,2,16,93,503,2736,15397,90556,558245, 3607387,24409819,172696471,1275310652,9813238958, 78548445033,652960116962,5628482431333, 50236822145840,463647958566143,4419123858908203, 43445718995990792,440083379418080388, 4588225614805060248] |