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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 6 |
| 3 | 16 |
| 4 | 61 |
| 5 | 212 |
| 6 | 753 |
| 7 | 2661 |
| 8 | 9415 |
| 9 | 33302 |
| 10 | 117802 |
| 11 | 416703 |
| 12 | 1474018 |
| 13 | 5214089 |
| 14 | 18443961 |
| 15 | 65242401 |
| 16 | 230783990 |
| 17 | 816359440 |
| 18 | 2887733833 |
| 19 | 10214871388 |
| 20 | 36133384697 |
| 21 | 127815754113 |
| 22 | 452126672783 |
| 23 | 1599321849338 |
| 24 | 5657331300590 |
[2,6,16,61,212,753,2661,9415,33302,117802,416703, 1474018,5214089,18443961,65242401,230783990, 816359440,2887733833,10214871388,36133384697, 127815754113,452126672783,1599321849338, 5657331300590] |