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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 4 |
| 5 | 17 |
| 6 | 66 |
| 7 | 252 |
| 8 | 946 |
| 9 | 3523 |
| 10 | 13054 |
| 11 | 48248 |
| 12 | 178146 |
| 13 | 657813 |
| 14 | 2430962 |
| 15 | 8995521 |
| 16 | 33342588 |
| 17 | 123822171 |
| 18 | 460772982 |
| 19 | 1718304786 |
| 20 | 6421729878 |
| 21 | 24051429321 |
| 22 | 90272123682 |
| 23 | 339522804129 |
| 24 | 1279556832780 |
| 25 | 4831639423695 |
| 26 | 18278491474726 |
| 27 | 69272752632502 |
| 28 | 262981858878706 |
[0,0,0,1,4,17,66,252,946,3523,13054,48248,178146, 657813,2430962,8995521,33342588,123822171, 460772982,1718304786,6421729878,24051429321, 90272123682,339522804129,1279556832780, 4831639423695,18278491474726,69272752632502, 262981858878706] |