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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 6 |
| 5 | 26 |
| 6 | 264 |
| 7 | 1157 |
| 8 | 23460 |
| 9 | 153485 |
| 10 | 6748424 |
| 11 | 70521609 |
| 12 | 6791578258 |
[0,0,1,6,26,264,1157,23460,153485,6748424, 70521609,6791578258] |