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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 2 |
| 3 | 4 |
| 4 | 16 |
| 5 | 78 |
| 6 | 458 |
| 7 | 3614 |
| 8 | 31418 |
| 9 | 315146 |
| 10 | 3566102 |
| 11 | 44827218 |
| 12 | 620168182 |
| 13 | 9347754294 |
| 14 | 152775554602 |
| 15 | 2687701571514 |
| 16 | 50670888880518 |
| 17 | 1018944127466708 |
| 18 | 21770157246285044 |
| 19 | 492495459066530344 |
| 20 | 11760335921226686984 |
| 21 | 295609024379492858260 |
| 22 | 7801944836722158839916 |
[2,2,4,16,78,458,3614,31418,315146,3566102, 44827218,620168182,9347754294,152775554602, 2687701571514,50670888880518,1018944127466708, 21770157246285044,492495459066530344, 11760335921226686984,295609024379492858260, 7801944836722158839916] |