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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 7 |
| 5 | 16 |
| 6 | 65 |
| 7 | 154 |
| 8 | 639 |
| 9 | 1520 |
| 10 | 6321 |
| 11 | 15042 |
| 12 | 62567 |
| 13 | 148896 |
| 14 | 619345 |
| 15 | 1473914 |
| 16 | 6130879 |
| 17 | 14590240 |
| 18 | 60689441 |
| 19 | 144428482 |
| 20 | 600763527 |
| 21 | 1429694576 |
| 22 | 5946945825 |
| 23 | 14152517274 |
| 24 | 58868694719 |
| 25 | 140095478160 |
| 26 | 582740001361 |
| 27 | 1386802264322 |
[0,1,2,7,16,65,154,639,1520,6321,15042,62567, 148896,619345,1473914,6130879,14590240,60689441, 144428482,600763527,1429694576,5946945825, 14152517274,58868694719,140095478160,582740001361, 1386802264322] |