| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 6 |
| 5 | 8 |
| 6 | 12 |
| 7 | 20 |
| 8 | 52 |
| 9 | 308 |
| 10 | 8500 |
| 11 | 2105652 |
| 12 | 17181974836 |
| 13 | 36028814200938804 |
| 14 | 618970019678718951650500916 |
| 15 | 22300745198530623760505737951367313156481332 |
[1,2,4,6,8,12,20,52,308,8500,2105652,17181974836, 36028814200938804,618970019678718951650500916, 22300745198530623760505737951367313156481332] |