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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 1 |
| 4 | 1 |
| 5 | 2 |
| 6 | 9 |
| 7 | 70 |
| 8 | 901 |
| 9 | 18851 |
| 10 | 640033 |
| 11 | 35182964 |
| 12 | 3130643763 |
| 13 | 450777518908 |
| 14 | 105028031261801 |
| 15 | 39595117008180069 |
| 16 | 24152916346958580289 |
| 17 | 23838888839331110565174 |
| 18 | 38070681323495436614002589 |
| 19 | 98374616701023368879472124802 |
| 20 | 411304234356297381789636339794573 |
[0,1,1,1,2,9,70,901,18851,640033,35182964, 3130643763,450777518908,105028031261801, 39595117008180069,24152916346958580289, 23838888839331110565174, 38070681323495436614002589, 98374616701023368879472124802, 411304234356297381789636339794573] |