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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 7 |
| 3 | 25 |
| 4 | 104 |
| 5 | 428 |
| 6 | 1881 |
| 7 | 8234 |
| 8 | 37201 |
| 9 | 168388 |
| 10 | 774534 |
| 11 | 3576978 |
| 12 | 16666951 |
| 13 | 77997784 |
| 14 | 366998557 |
| 15 | 1733533658 |
| 16 | 8218621913 |
| 17 | 39089929073 |
| 18 | 186433429979 |
| 19 | 891484661419 |
| 20 | 4272236389366 |
| 21 | 20516796321394 |
| 22 | 98708115461718 |
| 23 | 475708444814502 |
| 24 | 2296132506710913 |
| 25 | 11098671038754329 |
| 26 | 53717616206235570 |
| 27 | 260306492054452636 |
[1,2,7,25,104,428,1881,8234,37201,168388,774534, 3576978,16666951,77997784,366998557,1733533658, 8218621913,39089929073,186433429979,891484661419, 4272236389366,20516796321394,98708115461718, 475708444814502,2296132506710913, 11098671038754329,53717616206235570, 260306492054452636] |