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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 4 |
| 3 | 14 |
| 4 | 90 |
| 5 | 438 |
| 6 | 3151 |
| 7 | 24390 |
| 8 | 204156 |
| 9 | 1833212 |
| 10 | 17301306 |
| 11 | 175936764 |
| 12 | 1870247133 |
| 13 | 20872753540 |
| 14 | 243478609605 |
| 15 | 2957875659062 |
| 16 | 37319273049382 |
| 17 | 487266892836348 |
| 18 | 6574891059415183 |
| 19 | 91475580555526776 |
| 20 | 1309960647920094337 |
| 21 | 19278546942842385994 |
| 22 | 291167370195970990704 |
| 23 | 4507447478297070537800 |
[1,2,4,14,90,438,3151,24390,204156,1833212, 17301306,175936764,1870247133,20872753540, 243478609605,2957875659062,37319273049382, 487266892836348,6574891059415183, 91475580555526776,1309960647920094337, 19278546942842385994,291167370195970990704, 4507447478297070537800] |