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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 15 |
| 4 | 83 |
| 5 | 561 |
| 6 | 6332 |
| 7 | 88086 |
| 8 | 1561008 |
| 9 | 31966485 |
| 10 | 746278033 |
| 11 | 19441692751 |
| 12 | 559268543516 |
| 13 | 17599832876941 |
| 14 | 601468320356528 |
| 15 | 22182618618501188 |
| 16 | 878172760660077348 |
| 17 | 37144096971415045713 |
| 18 | 1671734397769302244110 |
| 19 | 79770632874353931073165 |
| 20 | 4022719642533206402716726 |
[1,4,15,83,561,6332,88086,1561008,31966485, 746278033,19441692751,559268543516,17599832876941, 601468320356528,22182618618501188, 878172760660077348,37144096971415045713, 1671734397769302244110,79770632874353931073165, 4022719642533206402716726] |