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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 21 |
| 5 | 72 |
| 6 | 236 |
| 7 | 745 |
| 8 | 2286 |
| 9 | 6866 |
| 10 | 20285 |
| 11 | 59156 |
| 12 | 170712 |
| 13 | 488401 |
| 14 | 1387226 |
| 15 | 3916062 |
| 16 | 10996581 |
| 17 | 30737760 |
| 18 | 85573316 |
| 19 | 237387961 |
| 20 | 656451270 |
| 21 | 1810142186 |
| 22 | 4978643597 |
| 23 | 13661617196 |
| 24 | 37409025456 |
| 25 | 102238082977 |
| 26 | 278920277426 |
| 27 | 759695287350 |
| 28 | 2066068144821 |
[1,2,6,21,72,236,745,2286,6866,20285,59156,170712, 488401,1387226,3916062,10996581,30737760,85573316, 237387961,656451270,1810142186,4978643597, 13661617196,37409025456,102238082977,278920277426, 759695287350,2066068144821] |