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| n | a(n) |
|---|---|
| 0 | 2 |
| 1 | 4 |
| 2 | 24 |
| 3 | 720 |
| 4 | 712800 |
| 5 | 666860040000 |
| 6 | 597568733024952150000000 |
| 7 | 474258018883889933710067708314342382812500000000 |
[2,4,24,720,712800,666860040000, 597568733024952150000000, 474258018883889933710067708314342382812500000000] |