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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 1 |
| 5 | 25 |
| 6 | 153 |
| 7 | 1076 |
| 8 | 13889 |
| 9 | 185108 |
| 10 | 4253039 |
| 11 | 156271576 |
| 12 | 7383352471 |
| 13 | 487631498606 |
[1,1,1,1,25,153,1076,13889,185108,4253039, 156271576,7383352471,487631498606] |