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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 21 |
| 3 | 180 |
| 4 | 3699 |
| 5 | 78186 |
| 6 | 1763689 |
| 7 | 40219584 |
| 8 | 921030783 |
| 9 | 21114454518 |
| 10 | 484210273013 |
| 11 | 11105346505100 |
| 12 | 254708804007115 |
| 13 | 5841980066693506 |
| 14 | 133991588716915713 |
| 15 | 3073232605116594392 |
| 16 | 70487720404861582487 |
| 17 | 1616707836356340649102 |
| 18 | 37080846132267449237645 |
[1,0,21,180,3699,78186,1763689,40219584,921030783, 21114454518,484210273013,11105346505100, 254708804007115,5841980066693506, 133991588716915713,3073232605116594392, 70487720404861582487,1616707836356340649102, 37080846132267449237645] |