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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 2 |
| 5 | 10 |
| 6 | 64 |
| 7 | 336 |
| 8 | 1872 |
| 9 | 11104 |
| 10 | 71944 |
| 11 | 508032 |
| 12 | 3511232 |
| 13 | 27192704 |
| 14 | 223750464 |
| 15 | 1947253504 |
| 16 | 17899536448 |
| 17 | 173156535168 |
| 18 | 1760383827776 |
| 19 | 18752453106176 |
| 20 | 209034916385472 |
| 21 | 2432351796434560 |
| 22 | 29509268795249700 |
[0,0,0,2,10,64,336,1872,11104,71944,508032, 3511232,27192704,223750464,1947253504,17899536448, 173156535168,1760383827776,18752453106176, 209034916385472,2432351796434560, 29509268795249700] |