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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 3 |
| 3 | 21 |
| 4 | 65 |
| 5 | 393 |
| 6 | 5907 |
| 7 | 17731 |
| 8 | 372411 |
| 9 | 2234571 |
| 10 | 20111419 |
| 11 | 20111503 |
| 12 | 663680439 |
| 13 | 1991042087 |
| 14 | 77650650633 |
| 15 | 33278851497 |
| 16 | 19967311127 |
| 17 | 119803867191 |
| 18 | 6109997233605 |
| 19 | 54989975121893 |
| 20 | 1044809527432655 |
| 21 | 15672142912044093 |
[0,3,21,65,393,5907,17731,372411,2234571,20111419, 20111503,663680439,1991042087,77650650633, 33278851497,19967311127,119803867191, 6109997233605,54989975121893,1044809527432655, 15672142912044093] |