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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 44 |
| 4 | 394 |
| 5 | 3948 |
| 6 | 42364 |
| 7 | 476120 |
| 8 | 5532714 |
| 9 | 65935804 |
| 10 | 801461012 |
| 11 | 9897836520 |
| 12 | 123840983812 |
| 13 | 1566487308344 |
| 14 | 19999112293944 |
| 15 | 257365488659376 |
| 16 | 3334967582746218 |
| 17 | 43477505482249692 |
| 18 | 569854228738577572 |
[1,2,6,44,394,3948,42364,476120,5532714,65935804, 801461012,9897836520,123840983812,1566487308344, 19999112293944,257365488659376,3334967582746218, 43477505482249692,569854228738577572] |