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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 13 |
| 4 | 42 |
| 5 | 132 |
| 6 | 428 |
| 7 | 1393 |
| 8 | 4561 |
| 9 | 15032 |
| 10 | 49889 |
| 11 | 166542 |
| 12 | 558744 |
| 13 | 1883028 |
| 14 | 6370957 |
| 15 | 21628455 |
| 16 | 73641852 |
| 17 | 251385571 |
| 18 | 860067894 |
| 19 | 2948380732 |
| 20 | 10124956970 |
| 21 | 34823894885 |
| 22 | 119940097035 |
| 23 | 413612099138 |
| 24 | 1427945022753 |
| 25 | 4934850614704 |
[1,4,13,42,132,428,1393,4561,15032,49889,166542, 558744,1883028,6370957,21628455,73641852, 251385571,860067894,2948380732,10124956970, 34823894885,119940097035,413612099138, 1427945022753,4934850614704] |