The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 3 |
| 3 | 33 |
| 4 | 180 |
| 5 | 611 |
| 6 | 1909 |
| 7 | 2340 |
| 8 | 12567 |
| 9 | 163797 |
| 10 | 879480 |
| 11 | 2996279 |
| 12 | 9346681 |
| 13 | 11463480 |
| 14 | 61551003 |
| 15 | 802279833 |
| 16 | 4307690700 |
| 17 | 14675777531 |
| 18 | 45780038029 |
| 19 | 56148124860 |
| 20 | 301476797967 |
| 21 | 3929566460397 |
| 22 | 21099068166960 |
| 23 | 71881955354159 |
| 24 | 224230616915761 |
[0,3,33,180,611,1909,2340,12567,163797,879480, 2996279,9346681,11463480,61551003,802279833, 4307690700,14675777531,45780038029,56148124860, 301476797967,3929566460397,21099068166960, 71881955354159,224230616915761] |