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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 6 |
| 3 | 56 |
| 4 | 1148 |
| 5 | 32056 |
| 6 | 1552272 |
| 7 | 127676872 |
| 8 | 18045771274 |
| 9 | 4495138018796 |
| 10 | 1955829240647962 |
| 11 | 1511334747222697904 |
| 12 | 2064152526111916503300 |
| 13 | 5022957354228609008158500 |
| 14 | 21748481726801956896608976098 |
[0,6,56,1148,32056,1552272,127676872,18045771274, 4495138018796,1955829240647962, 1511334747222697904,2064152526111916503300, 5022957354228609008158500, 21748481726801956896608976098] |