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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 21 |
| 4 | 73 |
| 5 | 261 |
| 6 | 957 |
| 7 | 3547 |
| 8 | 13267 |
| 9 | 50027 |
| 10 | 189780 |
| 11 | 723456 |
| 12 | 2769333 |
| 13 | 10637790 |
| 14 | 40984228 |
| 15 | 158306891 |
| 16 | 612856611 |
| 17 | 2377260192 |
| 18 | 9237543329 |
| 19 | 35951472496 |
| 20 | 140116098727 |
| 21 | 546778366195 |
| 22 | 2136168391753 |
| 23 | 8354417782742 |
| 24 | 32705042089703 |
[1,2,6,21,73,261,957,3547,13267,50027,189780, 723456,2769333,10637790,40984228,158306891, 612856611,2377260192,9237543329,35951472496, 140116098727,546778366195,2136168391753, 8354417782742,32705042089703] |