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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 11 |
| 5 | 51 |
| 6 | 287 |
| 7 | 1915 |
| 8 | 14684 |
| 9 | 127262 |
| 10 | 1230202 |
| 11 | 13122150 |
| 12 | 153091745 |
| 13 | 1939162101 |
| 14 | 26501882045 |
| 15 | 388694270000 |
| 16 | 6089543563341 |
| 17 | 101492392722343 |
| 18 | 1793032271428052 |
| 19 | 33469935733323642 |
| 20 | 658242069422031619 |
[1,1,1,3,11,51,287,1915,14684,127262,1230202, 13122150,153091745,1939162101,26501882045, 388694270000,6089543563341,101492392722343, 1793032271428052,33469935733323642, 658242069422031619] |