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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 18 |
| 2 | 1404 |
| 3 | 158760 |
| 4 | 21234150 |
| 5 | 3126159036 |
| 6 | 489778537248 |
| 7 | 80153987120064 |
| 8 | 13547671656870780 |
| 9 | 2347445149320843000 |
| 10 | 414851046001557525360 |
| 11 | 74499573518808987538080 |
| 12 | 13557818392046546526712440 |
| 13 | 2495117936356342079352318000 |
| 14 | 463604343771018075763879080000 |
| 15 | 86854813070150110063356637257600 |
[1,18,1404,158760,21234150,3126159036, 489778537248,80153987120064,13547671656870780, 2347445149320843000,414851046001557525360, 74499573518808987538080, 13557818392046546526712440, 2495117936356342079352318000, 463604343771018075763879080000, 86854813070150110063356637257600] |