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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 2 |
| 3 | 15 |
| 4 | 236 |
| 5 | 8490 |
| 6 | 459234 |
| 7 | 40325880 |
| 8 | 4777773104 |
| 9 | 767688946920 |
| 10 | 156746202491880 |
| 11 | 40056474754165320 |
| 12 | 12448131138826294152 |
| 13 | 4634982982962988690320 |
| 14 | 2033625840922821008112144 |
| 15 | 1039060311676326627685615800 |
| 16 | 611331728108400284878223051520 |
[1,0,2,15,236,8490,459234,40325880,4777773104, 767688946920,156746202491880,40056474754165320, 12448131138826294152,4634982982962988690320, 2033625840922821008112144, 1039060311676326627685615800, 611331728108400284878223051520] |