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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 18 |
| 3 | 148 |
| 4 | 1403 |
| 5 | 14417 |
| 6 | 156161 |
| 7 | 1755664 |
| 8 | 20293341 |
| 9 | 239654554 |
| 10 | 2879027132 |
| 11 | 35072400492 |
| 12 | 432238230583 |
| 13 | 5379422216020 |
| 14 | 67513288465855 |
| 15 | 853481985400772 |
| 16 | 10858099927189575 |
| 17 | 138912471444569435 |
| 18 | 1786014309638224994 |
| 19 | 23065160118446902506 |
| 20 | 299062458173041384523 |
[1,3,18,148,1403,14417,156161,1755664,20293341, 239654554,2879027132,35072400492,432238230583, 5379422216020,67513288465855,853481985400772, 10858099927189575,138912471444569435, 1786014309638224994,23065160118446902506, 299062458173041384523] |