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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 8 |
| 4 | 54 |
| 5 | 544 |
| 6 | 7508 |
| 7 | 133704 |
| 8 | 2943194 |
| 9 | 77589536 |
| 10 | 2391477804 |
| 11 | 84582890704 |
| 12 | 3382005372970 |
| 13 | 151034046369696 |
| 14 | 7458091839548356 |
| 15 | 403808650013237224 |
| 16 | 23801728042233670770 |
| 17 | 1517930142778063770304 |
| 18 | 104179592763803229618620 |
[1,1,2,8,54,544,7508,133704,2943194,77589536, 2391477804,84582890704,3382005372970, 151034046369696,7458091839548356, 403808650013237224,23801728042233670770, 1517930142778063770304,104179592763803229618620] |