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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 18 |
| 4 | -48 |
| 5 | -2630 |
| 6 | -52800 |
| 7 | -824054 |
| 8 | -8682240 |
| 9 | 54462258 |
| 10 | 7410631680 |
| 11 | 305163480578 |
| 12 | 8935815871488 |
| 13 | 167137193150954 |
| 14 | -1440976761090048 |
| 15 | -349400091225243270 |
| 16 | -22113174143289262080 |
| 17 | -960586728800597050526 |
| 18 | -26252145855684866211840 |
| 19 | 255024367557922004307442 |
[1,2,6,18,-48,-2630,-52800,-824054,-8682240, 54462258,7410631680,305163480578,8935815871488, 167137193150954,-1440976761090048, -349400091225243270,-22113174143289262080, -960586728800597050526,-26252145855684866211840, 255024367557922004307442] |