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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 5 |
| 3 | 20 |
| 4 | 137 |
| 5 | 1622 |
| 6 | 33293 |
| 7 | 1182440 |
| 8 | 72811793 |
| 9 | 7757988842 |
| 10 | 1433154521621 |
| 11 | 458101483131260 |
| 12 | 253879024041595289 |
| 13 | 243453910296759945662 |
| 14 | 404765167247068325944349 |
| 15 | 1164432505878183620543030480 |
[1,2,5,20,137,1622,33293,1182440,72811793, 7757988842,1433154521621,458101483131260, 253879024041595289,243453910296759945662, 404765167247068325944349, 1164432505878183620543030480] |