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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 73 |
| 3 | 222 |
| 4 | 5401 |
| 5 | 16425 |
| 6 | 399601 |
| 7 | 1215228 |
| 8 | 29565073 |
| 9 | 89910447 |
| 10 | 2187415801 |
| 11 | 6652157850 |
| 12 | 161839204201 |
| 13 | 492169770453 |
| 14 | 11973913695073 |
| 15 | 36413910855672 |
| 16 | 885907774231201 |
| 17 | 2694137233549275 |
| 18 | 65545201379413801 |
| 19 | 199329741371790678 |
| 20 | 4849458994302390073 |
[1,3,73,222,5401,16425,399601,1215228,29565073, 89910447,2187415801,6652157850,161839204201, 492169770453,11973913695073,36413910855672, 885907774231201,2694137233549275, 65545201379413801,199329741371790678, 4849458994302390073] |