The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 4 |
| 2 | 72 |
| 3 | 720 |
| 4 | 5600 |
| 5 | 37800 |
| 6 | 232848 |
| 7 | 1345344 |
| 8 | 7413120 |
| 9 | 39382200 |
| 10 | 203231600 |
| 11 | 1024287264 |
| 12 | 5062180032 |
| 13 | 24607819600 |
| 14 | 117942804000 |
| 15 | 558423072000 |
| 16 | 2615901857280 |
| 17 | 12139419556440 |
| 18 | 55866532906800 |
| 19 | 255192804636000 |
| 20 | 1157910842088000 |
| 21 | 5222177897816880 |
| 22 | 23422829664131040 |
[0,4,72,720,5600,37800,232848,1345344,7413120, 39382200,203231600,1024287264,5062180032, 24607819600,117942804000,558423072000, 2615901857280,12139419556440,55866532906800, 255192804636000,1157910842088000,5222177897816880, 23422829664131040] |