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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 10 |
| 4 | 31 |
| 5 | 101 |
| 6 | 336 |
| 7 | 1128 |
| 8 | 3823 |
| 9 | 13051 |
| 10 | 44803 |
| 11 | 154518 |
| 12 | 534964 |
| 13 | 1858156 |
| 14 | 6472168 |
| 15 | 22597760 |
| 16 | 79067375 |
| 17 | 277164295 |
| 18 | 973184313 |
| 19 | 3422117190 |
| 20 | 12049586631 |
| 21 | 42478745781 |
| 22 | 149915252028 |
| 23 | 529606271560 |
| 24 | 1872653175556 |
| 25 | 6627147599476 |
| 26 | 23471065878276 |
| 27 | 83186110269928 |
[1,1,3,10,31,101,336,1128,3823,13051,44803,154518, 534964,1858156,6472168,22597760,79067375, 277164295,973184313,3422117190,12049586631, 42478745781,149915252028,529606271560, 1872653175556,6627147599476,23471065878276, 83186110269928] |