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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 22 |
| 3 | 103 |
| 4 | 484 |
| 5 | 2270 |
| 6 | 10648 |
| 7 | 49943 |
| 8 | 234256 |
| 9 | 1098758 |
| 10 | 5153632 |
| 11 | 24172676 |
| 12 | 113379904 |
| 13 | 531798888 |
| 14 | 2494357888 |
| 15 | 11699575548 |
| 16 | 54875873536 |
| 17 | 257390662067 |
| 18 | 1207269217792 |
| 19 | 5662594565481 |
| 20 | 26559922791424 |
[1,4,22,103,484,2270,10648,49943,234256,1098758, 5153632,24172676,113379904,531798888,2494357888, 11699575548,54875873536,257390662067, 1207269217792,5662594565481,26559922791424] |