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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 2 |
| 3 | 6 |
| 4 | 17 |
| 5 | 55 |
| 6 | 207 |
| 7 | 882 |
| 8 | 4146 |
| 9 | 21154 |
| 10 | 115983 |
| 11 | 678579 |
| 12 | 4213607 |
| 13 | 27644448 |
| 14 | 190899334 |
| 15 | 1382958558 |
| 16 | 10480142161 |
| 17 | 82864869819 |
| 18 | 682076806175 |
| 19 | 5832742205074 |
| 20 | 51724158235390 |
| 21 | 474869816156770 |
| 22 | 4506715738447343 |
| 23 | 44152005855084367 |
| 24 | 445958869294805311 |
| 25 | 4638590332229999376 |
[0,2,6,17,55,207,882,4146,21154,115983,678579, 4213607,27644448,190899334,1382958558,10480142161, 82864869819,682076806175,5832742205074, 51724158235390,474869816156770,4506715738447343, 44152005855084367,445958869294805311, 4638590332229999376] |