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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 15 |
| 4 | 207 |
| 5 | 3283 |
| 6 | 64650 |
| 7 | 1640007 |
| 8 | 54704700 |
| 9 | 2429994600 |
| 10 | 144950275305 |
| 11 | 11678538065077 |
| 12 | 1276251983814717 |
| 13 | 189767651505152535 |
| 14 | 38484504169958401936 |
| 15 | 10664509514660169498882 |
| 16 | 4044220867954839169651680 |
[0,1,15,207,3283,64650,1640007,54704700, 2429994600,144950275305,11678538065077, 1276251983814717,189767651505152535, 38484504169958401936,10664509514660169498882, 4044220867954839169651680] |