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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 19 |
| 5 | 150 |
| 6 | 1497 |
| 7 | 17955 |
| 8 | 251681 |
| 9 | 4036284 |
| 10 | 72874125 |
| 11 | 1462571055 |
| 12 | 32297755803 |
| 13 | 778188449610 |
| 14 | 20313917363733 |
| 15 | 571081958323695 |
| 16 | 17201321168216385 |
| 17 | 552635193533958360 |
| 18 | 18863471310967732473 |
| 19 | 681711909339186154395 |
| 20 | 26003437607893415476995 |
[1,0,1,3,19,150,1497,17955,251681,4036284, 72874125,1462571055,32297755803,778188449610, 20313917363733,571081958323695,17201321168216385, 552635193533958360,18863471310967732473, 681711909339186154395,26003437607893415476995] |