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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 12 |
| 3 | 52 |
| 4 | 236 |
| 5 | 1108 |
| 6 | 5340 |
| 7 | 26276 |
| 8 | 131484 |
| 9 | 667108 |
| 10 | 3424108 |
| 11 | 17748564 |
| 12 | 92776716 |
| 13 | 488527284 |
| 14 | 2588907708 |
| 15 | 13797337668 |
| 16 | 73901315644 |
| 17 | 397609958596 |
| 18 | 2147904635340 |
| 19 | 11645489540468 |
| 20 | 63349140877356 |
| 21 | 345651184335892 |
| 22 | 1891209255293852 |
[1,3,12,52,236,1108,5340,26276,131484,667108, 3424108,17748564,92776716,488527284,2588907708, 13797337668,73901315644,397609958596, 2147904635340,11645489540468,63349140877356, 345651184335892,1891209255293852] |