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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 33 |
| 4 | 420 |
| 5 | 7305 |
| 6 | 162198 |
| 7 | 4398933 |
| 8 | 141259912 |
| 9 | 5248415169 |
| 10 | 221637262410 |
| 11 | 10489037239989 |
| 12 | 549976658760972 |
| 13 | 31650208550358801 |
| 14 | 1983383546128436494 |
| 15 | 134440159552418677365 |
| 16 | 9800566084124471843472 |
| 17 | 764564284108064457174273 |
| 18 | 63552209174719502953891986 |
[1,4,33,420,7305,162198,4398933,141259912, 5248415169,221637262410,10489037239989, 549976658760972,31650208550358801, 1983383546128436494,134440159552418677365, 9800566084124471843472,764564284108064457174273, 63552209174719502953891986] |