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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 9 |
| 5 | 23 |
| 6 | 59 |
| 7 | 153 |
| 8 | 406 |
| 9 | 1126 |
| 10 | 3124 |
| 11 | 8684 |
| 12 | 24202 |
| 13 | 67640 |
| 14 | 189576 |
| 15 | 532786 |
| 16 | 1519151 |
| 17 | 4356471 |
| 18 | 12501301 |
| 19 | 35901325 |
| 20 | 103188123 |
| 21 | 296844379 |
| 22 | 854701935 |
| 23 | 2463133311 |
| 24 | 7104685935 |
| 25 | 20510632575 |
| 26 | 59262772629 |
| 27 | 172271893036 |
| 28 | 502157965938 |
[1,1,2,4,9,23,59,153,406,1126,3124,8684,24202, 67640,189576,532786,1519151,4356471,12501301, 35901325,103188123,296844379,854701935,2463133311, 7104685935,20510632575,59262772629,172271893036, 502157965938] |