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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 9 |
| 5 | 24 |
| 6 | 68 |
| 7 | 204 |
| 8 | 642 |
| 9 | 2096 |
| 10 | 7026 |
| 11 | 24026 |
| 12 | 83454 |
| 13 | 293562 |
| 14 | 1043488 |
| 15 | 3741954 |
| 16 | 13520253 |
| 17 | 49171485 |
| 18 | 179859763 |
| 19 | 661240417 |
| 20 | 2442023860 |
| 21 | 9055315765 |
| 22 | 33701442548 |
| 23 | 125845246605 |
| 24 | 471346884115 |
| 25 | 1770306347204 |
| 26 | 6665954191204 |
| 27 | 25159152509961 |
[1,2,4,9,24,68,204,642,2096,7026,24026,83454, 293562,1043488,3741954,13520253,49171485, 179859763,661240417,2442023860,9055315765, 33701442548,125845246605,471346884115, 1770306347204,6665954191204,25159152509961] |