The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 27 |
| 4 | 288 |
| 5 | 2250 |
| 6 | 15795 |
| 7 | 105987 |
| 8 | 696864 |
| 9 | 4540968 |
| 10 | 29490750 |
| 11 | 191420427 |
| 12 | 1243565235 |
| 13 | 8091223647 |
| 14 | 52739879283 |
| 15 | 344402073027 |
| 16 | 2253045672480 |
| 17 | 14764068268068 |
| 18 | 96899123172708 |
| 19 | 636877933530303 |
| 20 | 4191430966219038 |
| 21 | 27617820628739718 |
| 22 | 182176855684869243 |
[0,0,27,288,2250,15795,105987,696864,4540968, 29490750,191420427,1243565235,8091223647, 52739879283,344402073027,2253045672480, 14764068268068,96899123172708,636877933530303, 4191430966219038,27617820628739718, 182176855684869243] |