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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 2 |
| 3 | 3 |
| 4 | 28 |
| 5 | 185 |
| 6 | 1566 |
| 7 | 18277 |
| 8 | 218744 |
| 9 | 3206961 |
| 10 | 52134490 |
| 11 | 935303501 |
| 12 | 18733723812 |
| 13 | 406458491881 |
| 14 | 9598660337462 |
| 15 | 244471271572725 |
| 16 | 6671672053304176 |
| 17 | 194631575264393057 |
| 18 | 6036199529439919410 |
| 19 | 198427339307102272669 |
| 20 | 6892068588221322730460 |
[1,0,2,3,28,185,1566,18277,218744,3206961, 52134490,935303501,18733723812,406458491881, 9598660337462,244471271572725,6671672053304176, 194631575264393057,6036199529439919410, 198427339307102272669,6892068588221322730460] |