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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 22 |
| 5 | 89 |
| 6 | 368 |
| 7 | 1488 |
| 8 | 5831 |
| 9 | 22311 |
| 10 | 84223 |
| 11 | 316181 |
| 12 | 1185884 |
| 13 | 4452567 |
| 14 | 16742230 |
| 15 | 63025805 |
| 16 | 237423928 |
| 17 | 894681874 |
| 18 | 3371727204 |
| 19 | 12706639594 |
| 20 | 47884046357 |
| 21 | 180440982667 |
| 22 | 679939553548 |
| 23 | 2562134671440 |
| 24 | 9654584875285 |
| 25 | 36380338185856 |
| 26 | 137088669193146 |
[1,1,2,6,22,89,368,1488,5831,22311,84223,316181, 1185884,4452567,16742230,63025805,237423928, 894681874,3371727204,12706639594,47884046357, 180440982667,679939553548,2562134671440, 9654584875285,36380338185856,137088669193146] |