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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 2 |
| 5 | 12 |
| 6 | 56 |
| 7 | 282 |
| 8 | 1365 |
| 9 | 6666 |
| 10 | 32002 |
| 11 | 153350 |
| 12 | 731156 |
| 13 | 3480594 |
| 14 | 16546884 |
| 15 | 78644579 |
| 16 | 373813930 |
| 17 | 1777680136 |
| 18 | 8459543997 |
| 19 | 40290717546 |
| 20 | 192072529566 |
| 21 | 916541991433 |
| 22 | 4378019950311 |
| 23 | 20933668637794 |
| 24 | 100196639221232 |
[0,0,0,1,2,12,56,282,1365,6666,32002,153350, 731156,3480594,16546884,78644579,373813930, 1777680136,8459543997,40290717546,192072529566, 916541991433,4378019950311,20933668637794, 100196639221232] |