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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 8 |
| 3 | 37 |
| 4 | 179 |
| 5 | 881 |
| 6 | 4369 |
| 7 | 21746 |
| 8 | 108444 |
| 9 | 541362 |
| 10 | 2704158 |
| 11 | 13512392 |
| 12 | 67534828 |
| 13 | 337584992 |
| 14 | 1687627800 |
| 15 | 8437136085 |
| 16 | 42182258715 |
| 17 | 210899507685 |
| 18 | 1054456597965 |
| 19 | 5272139698215 |
| 20 | 26360193558735 |
| 21 | 131799177579015 |
[1,2,8,37,179,881,4369,21746,108444,541362, 2704158,13512392,67534828,337584992,1687627800, 8437136085,42182258715,210899507685,1054456597965, 5272139698215,26360193558735,131799177579015] |