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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 2 |
| 5 | 12 |
| 6 | 43 |
| 7 | 174 |
| 8 | 657 |
| 9 | 2571 |
| 10 | 9911 |
| 11 | 38633 |
| 12 | 150437 |
| 13 | 588544 |
| 14 | 2306204 |
| 15 | 9061179 |
| 16 | 35665587 |
| 17 | 140648710 |
| 18 | 555514177 |
| 19 | 2197298561 |
| 20 | 8702439446 |
| 21 | 34506900216 |
| 22 | 136972867380 |
| 23 | 544237912916 |
| 24 | 2164377093376 |
| 25 | 8614630304437 |
[0,0,1,2,12,43,174,657,2571,9911,38633,150437, 588544,2306204,9061179,35665587,140648710, 555514177,2197298561,8702439446,34506900216, 136972867380,544237912916,2164377093376, 8614630304437] |