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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 17 |
| 6 | 127 |
| 7 | 941 |
| 8 | 6662 |
| 9 | 47771 |
| 10 | 344708 |
| 11 | 2518713 |
| 12 | 18585455 |
| 13 | 138434899 |
| 14 | 1039401564 |
| 15 | 7859310749 |
| 16 | 59794417068 |
| 17 | 457408090798 |
| 18 | 3516003907738 |
| 19 | 27144132395911 |
| 20 | 210375321159360 |
| 21 | 1636229683680890 |
| 22 | 12766881894462441 |
[0,0,0,1,17,127,941,6662,47771,344708,2518713, 18585455,138434899,1039401564,7859310749, 59794417068,457408090798,3516003907738, 27144132395911,210375321159360,1636229683680890, 12766881894462441] |