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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 6 |
| 2 | 42 |
| 3 | 258 |
| 4 | 1770 |
| 5 | 11058 |
| 6 | 74778 |
| 7 | 472866 |
| 8 | 3164874 |
| 9 | 20188050 |
| 10 | 134123514 |
| 11 | 860893314 |
| 12 | 5689339818 |
| 13 | 36681499122 |
| 14 | 241497732570 |
| 15 | 1562031700962 |
| 16 | 10255950073482 |
| 17 | 66489091308114 |
| 18 | 435703293953466 |
| 19 | 2829310581045570 |
[1,6,42,258,1770,11058,74778,472866,3164874, 20188050,134123514,860893314,5689339818, 36681499122,241497732570,1562031700962, 10255950073482,66489091308114,435703293953466, 2829310581045570] |