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| n | a(n) |
|---|---|
| 1 | 20 |
| 2 | 16260 |
| 3 | 20933840 |
| 4 | 33833709700 |
| 5 | 62810128195920 |
| 6 | 127676780106968400 |
| 7 | 276686670102097569600 |
| 8 | 628807365128705353776900 |
| 9 | 1482500191777802616831698000 |
| 10 | 3598791496054686645936395190160 |
[20,16260,20933840,33833709700,62810128195920, 127676780106968400,276686670102097569600, 628807365128705353776900, 1482500191777802616831698000, 3598791496054686645936395190160] |