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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 5 |
| 4 | 20 |
| 5 | 70 |
| 6 | 222 |
| 7 | 654 |
| 8 | 1817 |
| 9 | 4815 |
| 10 | 12265 |
| 11 | 30217 |
| 12 | 72344 |
| 13 | 168950 |
| 14 | 386050 |
| 15 | 865264 |
| 16 | 1906260 |
| 17 | 4135320 |
| 18 | 8846700 |
| 19 | 18687800 |
| 20 | 39023300 |
| 21 | 80630770 |
| 22 | 164990461 |
| 23 | 334599050 |
| 24 | 672958200 |
| 25 | 1343096325 |
| 26 | 2661417579 |
| 27 | 5238577803 |
| 28 | 10246976040 |
| 29 | 19926439195 |
[0,1,5,20,70,222,654,1817,4815,12265,30217,72344, 168950,386050,865264,1906260,4135320,8846700, 18687800,39023300,80630770,164990461,334599050, 672958200,1343096325,2661417579,5238577803, 10246976040,19926439195] |