The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 52 |
| 3 | 1264 |
| 4 | 48592 |
| 5 | 2703424 |
| 6 | 205421632 |
| 7 | 20447497984 |
| 8 | 2582830012672 |
| 9 | 403755759698944 |
| 10 | 76538801941107712 |
| 11 | 17301582442235490304 |
| 12 | 4598285794418840522752 |
| 13 | 1419656731675234066776064 |
| 14 | 503894206909911797902753792 |
| 15 | 203768397954530049098393780224 |
[1,4,52,1264,48592,2703424,205421632,20447497984, 2582830012672,403755759698944,76538801941107712, 17301582442235490304,4598285794418840522752, 1419656731675234066776064, 503894206909911797902753792, 203768397954530049098393780224] |