The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 4 |
| 3 | 4 |
| 4 | 56 |
| 5 | 56 |
| 6 | 616 |
| 7 | 8008 |
| 8 | 16016 |
| 9 | 816816 |
| 10 | 5173168 |
| 11 | 5173168 |
| 12 | 118982864 |
| 13 | 118982864 |
| 14 | 356948592 |
| 15 | 3450503056 |
| 16 | 213931189472 |
| 17 | 19448289952 |
| 18 | 58344869856 |
| 19 | 719586728224 |
| 20 | 719586728224 |
| 21 | 4214722265312 |
| 22 | 1993563631492576 |
| 23 | 1993563631492576 |
[2,4,4,56,56,616,8008,16016,816816,5173168, 5173168,118982864,118982864,356948592,3450503056, 213931189472,19448289952,58344869856,719586728224, 719586728224,4214722265312,1993563631492576, 1993563631492576] |