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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 2 |
| 6 | 13 |
| 7 | 50 |
| 8 | 220 |
| 9 | 866 |
| 10 | 3435 |
| 11 | 13250 |
| 12 | 51061 |
| 13 | 194810 |
| 14 | 742601 |
| 15 | 2823764 |
| 16 | 10738660 |
| 17 | 40843370 |
| 18 | 155493872 |
| 19 | 592614050 |
| 20 | 2261622287 |
| 21 | 8643289484 |
| 22 | 33080907357 |
| 23 | 126797503250 |
| 24 | 486710920300 |
| 25 | 1870851589552 |
[0,0,0,1,2,13,50,220,866,3435,13250,51061,194810, 742601,2823764,10738660,40843370,155493872, 592614050,2261622287,8643289484,33080907357, 126797503250,486710920300,1870851589552] |