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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 16 |
| 5 | 51 |
| 6 | 195 |
| 7 | 932 |
| 8 | 5651 |
| 9 | 43641 |
| 10 | 428905 |
| 11 | 5362388 |
| 12 | 85303080 |
| 13 | 1726416461 |
| 14 | 44444215422 |
| 15 | 1455335603434 |
| 16 | 60619535173748 |
| 17 | 3211914908993651 |
| 18 | 216474718772864071 |
| 19 | 18558435268379931580 |
| 20 | 2023812522812259857355 |
[1,2,6,16,51,195,932,5651,43641,428905,5362388, 85303080,1726416461,44444215422,1455335603434, 60619535173748,3211914908993651, 216474718772864071,18558435268379931580, 2023812522812259857355] |