The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 4 |
| 3 | 12 |
| 4 | 48 |
| 5 | 240 |
| 6 | 10 |
| 7 | 70 |
| 8 | 560 |
| 9 | 54 |
| 10 | 540 |
| 11 | 5940 |
| 12 | 71280 |
| 13 | 9240 |
| 14 | 129360 |
| 15 | 19 |
| 16 | 304 |
| 17 | 5168 |
| 18 | 93024 |
| 19 | 145 |
| 20 | 29 |
| 21 | 609 |
| 22 | 198 |
| 23 | 0 |
[2,4,12,48,240,10,70,560,54,540,5940,71280,9240, 129360,19,304,5168,93024,145,29,609,198,0] |