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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | -3 |
| 3 | -16 |
| 4 | 60 |
| 5 | 384 |
| 6 | -1680 |
| 7 | -12288 |
| 8 | 60480 |
| 9 | 491520 |
| 10 | -2661120 |
| 11 | -23592960 |
| 12 | 138378240 |
| 13 | 1321205760 |
| 14 | -8302694400 |
| 15 | -84557168640 |
| 16 | 564583219200 |
| 17 | 6088116142080 |
| 18 | -42908324659200 |
| 19 | -487049291366400 |
| 20 | 3604299271372800 |
[1,-3,-16,60,384,-1680,-12288,60480,491520, -2661120,-23592960,138378240,1321205760, -8302694400,-84557168640,564583219200, 6088116142080,-42908324659200,-487049291366400, 3604299271372800] |