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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 7 |
| 5 | 23 |
| 6 | 55 |
| 7 | 247 |
| 8 | 1015 |
| 9 | 5623 |
| 10 | 24055 |
| 11 | 208375 |
| 12 | 945655 |
| 13 | 9793015 |
| 14 | 62877175 |
| 15 | 487550455 |
| 16 | 3884936695 |
| 17 | 58243116535 |
| 18 | 384392195575 |
| 19 | 6255075618295 |
| 20 | 53220543000055 |
| 21 | 616806151581175 |
| 22 | 6252662237392375 |
| 23 | 130241496125238775 |
| 24 | 1122152167228009975 |
| 25 | 20960365589283433975 |
[0,1,3,7,23,55,247,1015,5623,24055,208375,945655, 9793015,62877175,487550455,3884936695,58243116535, 384392195575,6255075618295,53220543000055, 616806151581175,6252662237392375, 130241496125238775,1122152167228009975, 20960365589283433975] |