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| n | a(n) |
|---|---|
| 2 | 1 |
| 3 | 4 |
| 4 | 34 |
| 5 | 436 |
| 6 | 7428 |
| 7 | 157368 |
| 8 | 3980688 |
| 9 | 116949600 |
| 10 | 3911421600 |
| 11 | 146673662400 |
| 12 | 6093249563520 |
| 13 | 277729608280320 |
| 14 | 13778539159795200 |
| 15 | 739059210587980800 |
| 16 | 42615627311477606400 |
| 17 | 2628646012982829772800 |
| 18 | 172704619437756321484800 |
[1,4,34,436,7428,157368,3980688,116949600, 3911421600,146673662400,6093249563520, 277729608280320,13778539159795200, 739059210587980800,42615627311477606400, 2628646012982829772800,172704619437756321484800] |