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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 18 |
| 5 | 66 |
| 6 | 252 |
| 7 | 1176 |
| 8 | 5768 |
| 9 | 34216 |
| 10 | 209552 |
| 11 | 1521696 |
| 12 | 11196768 |
| 13 | 96160416 |
| 14 | 825730752 |
| 15 | 8183634816 |
| 16 | 80315504768 |
| 17 | 902135948416 |
| 18 | 9960471556352 |
| 19 | 125042593153536 |
| 20 | 1533993841632768 |
| 21 | 21284696790729216 |
| 22 | 287227371473636352 |
| 23 | 4364939476603385856 |
[1,1,2,6,18,66,252,1176,5768,34216,209552,1521696, 11196768,96160416,825730752,8183634816, 80315504768,902135948416,9960471556352, 125042593153536,1533993841632768, 21284696790729216,287227371473636352, 4364939476603385856] |