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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 8 |
| 4 | 37 |
| 5 | 219 |
| 6 | 1557 |
| 7 | 12994 |
| 8 | 124427 |
| 9 | 1344506 |
| 10 | 16178891 |
| 11 | 214522339 |
| 12 | 3107144562 |
| 13 | 48805300668 |
| 14 | 826268787588 |
| 15 | 14998055299920 |
| 16 | 290550119360174 |
| 17 | 5983278021430064 |
| 18 | 130512410617529321 |
| 19 | 3006012061455129053 |
| 20 | 72900477505718600661 |
[1,1,2,8,37,219,1557,12994,124427,1344506, 16178891,214522339,3107144562,48805300668, 826268787588,14998055299920,290550119360174, 5983278021430064,130512410617529321, 3006012061455129053,72900477505718600661] |