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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 26 |
| 5 | 133 |
| 6 | 905 |
| 7 | 6521 |
| 8 | 57126 |
| 9 | 544820 |
| 10 | 5878219 |
| 11 | 66851119 |
| 12 | 881424550 |
| 13 | 11803494823 |
| 14 | 175906313032 |
| 15 | 2767829058956 |
| 16 | 47008174824136 |
| 17 | 821285150996811 |
| 18 | 15816596073011143 |
| 19 | 308160754687446289 |
| 20 | 6498330632792677804 |
[1,2,6,26,133,905,6521,57126,544820,5878219, 66851119,881424550,11803494823,175906313032, 2767829058956,47008174824136,821285150996811, 15816596073011143,308160754687446289, 6498330632792677804] |