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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 3 |
| 5 | 15 |
| 6 | 97 |
| 7 | 597 |
| 8 | 5098 |
| 9 | 47746 |
| 10 | 582342 |
| 11 | 7691278 |
| 12 | 125339157 |
| 13 | 2195109753 |
| 14 | 45664819407 |
| 15 | 1013323126923 |
| 16 | 26022340062564 |
| 17 | 709267685968788 |
| 18 | 21939269071805596 |
| 19 | 717007984481424300 |
| 20 | 26196923530426606903 |
[0,0,0,3,15,97,597,5098,47746,582342,7691278, 125339157,2195109753,45664819407,1013323126923, 26022340062564,709267685968788,21939269071805596, 717007984481424300,26196923530426606903] |