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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 5 |
| 5 | 14 |
| 6 | 43 |
| 7 | 140 |
| 8 | 475 |
| 9 | 1660 |
| 10 | 5932 |
| 11 | 21570 |
| 12 | 79541 |
| 13 | 296732 |
| 14 | 1117827 |
| 15 | 4246248 |
| 16 | 16246794 |
| 17 | 62555600 |
| 18 | 242201234 |
| 19 | 942384808 |
| 20 | 3682943857 |
| 21 | 14450545764 |
| 22 | 56902437222 |
| 23 | 224798143444 |
| 24 | 890730315852 |
| 25 | 3539022858268 |
| 26 | 14096429070015 |
| 27 | 56278104658078 |
| 28 | 225164436942220 |
[1,1,2,5,14,43,140,475,1660,5932,21570,79541, 296732,1117827,4246248,16246794,62555600, 242201234,942384808,3682943857,14450545764, 56902437222,224798143444,890730315852, 3539022858268,14096429070015,56278104658078, 225164436942220] |