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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 2 |
| 3 | 36 |
| 4 | 624 |
| 5 | 11800 |
| 6 | 248400 |
| 7 | 5817084 |
| 8 | 150660608 |
| 9 | 4285808496 |
| 10 | 133010784000 |
| 11 | 4475982692500 |
| 12 | 162419627132928 |
| 13 | 6324111407554824 |
| 14 | 263067938335913984 |
| 15 | 11645155099754347500 |
| 16 | 546652030933421260800 |
| 17 | 27126781579050558916576 |
| 18 | 1418971858887930496745472 |
[0,2,36,624,11800,248400,5817084,150660608, 4285808496,133010784000,4475982692500, 162419627132928,6324111407554824, 263067938335913984,11645155099754347500, 546652030933421260800,27126781579050558916576, 1418971858887930496745472] |