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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 31 |
| 5 | 195 |
| 6 | 2182 |
| 7 | 30100 |
| 8 | 529674 |
| 9 | 10778125 |
| 10 | 250155012 |
| 11 | 6484839306 |
| 12 | 185757443582 |
| 13 | 5824538174455 |
| 14 | 198428907905336 |
| 15 | 7298232189810696 |
| 16 | 288230385949610020 |
| 17 | 12165298000307625609 |
| 18 | 546477890436083284338 |
| 19 | 26031837576091248872110 |
| 20 | 1310720000028416000168044 |
[1,1,2,6,31,195,2182,30100,529674,10778125, 250155012,6484839306,185757443582,5824538174455, 198428907905336,7298232189810696, 288230385949610020,12165298000307625609, 546477890436083284338,26031837576091248872110, 1310720000028416000168044] |