The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 12 |
| 3 | 66 |
| 4 | 480 |
| 5 | 4368 |
| 6 | 47712 |
| 7 | 608016 |
| 8 | 8855040 |
| 9 | 145083648 |
| 10 | 2641216512 |
| 11 | 52891055616 |
| 12 | 1155444326400 |
| 13 | 27344999497728 |
| 14 | 696933753434112 |
| 15 | 19031293222127616 |
| 16 | 554336947975618560 |
| 17 | 17155693983744196608 |
| 18 | 562168282464340672512 |
| 19 | 19444889661250162262016 |
[1,3,12,66,480,4368,47712,608016,8855040, 145083648,2641216512,52891055616,1155444326400, 27344999497728,696933753434112,19031293222127616, 554336947975618560,17155693983744196608, 562168282464340672512,19444889661250162262016] |