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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 20 |
| 3 | 27720 |
| 4 | 5173168 |
| 5 | 2329089562800 |
| 6 | 2844937529085600 |
| 7 | 54749786241679275146400 |
| 8 | 1874681189225708508850515710400 |
| 9 | 718766754945489455304472257065075294400 |
| 10 | 153803387341307877636928566091115101174034840640 |
[2,20,27720,5173168,2329089562800, 2844937529085600,54749786241679275146400, 1874681189225708508850515710400, 718766754945489455304472257065075294400, 153803387341307877636928566091115101174034840640] |