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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 12 |
| 4 | 210 |
| 5 | 4290 |
| 6 | 42840 |
| 7 | 4037880 |
| 8 | 73628100 |
| 9 | 17226649440 |
| 10 | 422630873280 |
| 11 | 37569227295600 |
| 12 | 25278012283043520 |
| 13 | 37342441057521600 |
| 14 | 1860812172555592576320 |
| 15 | 6714127941651376646400 |
| 16 | 13782919836150390515990400 |
| 17 | 1090799084645723774857536000 |
[1,4,12,210,4290,42840,4037880,73628100, 17226649440,422630873280,37569227295600, 25278012283043520,37342441057521600, 1860812172555592576320,6714127941651376646400, 13782919836150390515990400, 1090799084645723774857536000] |