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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 4 |
| 5 | 20 |
| 6 | 65 |
| 7 | 175 |
| 8 | 742 |
| 9 | 2604 |
| 10 | 9072 |
| 11 | 36960 |
| 12 | 139392 |
| 13 | 538824 |
| 14 | 2198625 |
| 15 | 8735727 |
| 16 | 35456850 |
| 17 | 146812952 |
| 18 | 604215326 |
| 19 | 2521642266 |
| 20 | 10617725768 |
| 21 | 44760668160 |
| 22 | 190357768328 |
| 23 | 813800295880 |
| 24 | 3490232753680 |
| 25 | 15055389124320 |
| 26 | 65193213272800 |
| 27 | 283254330047520 |
| 28 | 1235731377864960 |
| 29 | 5407996483238160 |
[1,0,1,3,4,20,65,175,742,2604,9072,36960,139392, 538824,2198625,8735727,35456850,146812952, 604215326,2521642266,10617725768,44760668160, 190357768328,813800295880,3490232753680, 15055389124320,65193213272800,283254330047520, 1235731377864960,5407996483238160] |