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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 24 |
| 4 | 94 |
| 5 | 374 |
| 6 | 1520 |
| 7 | 6252 |
| 8 | 25942 |
| 9 | 108408 |
| 10 | 455586 |
| 11 | 1923444 |
| 12 | 8151856 |
| 13 | 34661252 |
| 14 | 147788484 |
| 15 | 631660788 |
| 16 | 2705471254 |
| 17 | 11609393084 |
| 18 | 49899207640 |
| 19 | 214792704256 |
| 20 | 925811868178 |
| 21 | 3995288307392 |
| 22 | 17260287754284 |
| 23 | 74641620619072 |
| 24 | 323080683587056 |
| 25 | 1399606566298916 |
[1,2,6,24,94,374,1520,6252,25942,108408,455586, 1923444,8151856,34661252,147788484,631660788, 2705471254,11609393084,49899207640,214792704256, 925811868178,3995288307392,17260287754284, 74641620619072,323080683587056,1399606566298916] |