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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 9 |
| 5 | 26 |
| 6 | 108 |
| 7 | 785 |
| 8 | 12450 |
| 9 | 628676 |
| 10 | 155631177 |
| 11 | 395389144154 |
| 12 | 24221458643549484 |
| 13 | 156332599536291235925201 |
| 14 | 586679058977510608947573592591458 |
| 15 | 24439881677774993432884951095586547256059481860 |
[0,1,2,4,9,26,108,785,12450,628676,155631177, 395389144154,24221458643549484, 156332599536291235925201, 586679058977510608947573592591458, 24439881677774993432884951095586547256059481860] |