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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 6 |
| 3 | 87 |
| 4 | 4288 |
| 5 | 433045 |
| 6 | 70899306 |
| 7 | 16947087955 |
| 8 | 5544027333440 |
| 9 | 2372735984247009 |
| 10 | 1284753824984593630 |
| 11 | 857573459327085778431 |
| 12 | 691208427837113229333984 |
| 13 | 661423852799242010825878453 |
[0,1,6,87,4288,433045,70899306,16947087955, 5544027333440,2372735984247009, 1284753824984593630,857573459327085778431, 691208427837113229333984, 661423852799242010825878453] |