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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 10 |
| 3 | 2780 |
| 4 | 6631556521 |
| 5 | 71669271794142235712392433 |
| 6 | 78417479379491793666843945562521255790293292270929676484784808001 |
[0,1,10,2780,6631556521, 71669271794142235712392433, 78417479379491793666843945562521255790293292270929\ 676484784808001] |