The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 32 |
| 3 | 220 |
| 4 | 1578 |
| 5 | 11303 |
| 6 | 81105 |
| 7 | 582032 |
| 8 | 4177161 |
| 9 | 29979239 |
| 10 | 215160247 |
| 11 | 1544201029 |
| 12 | 11082704750 |
| 13 | 79540390044 |
| 14 | 570860083491 |
| 15 | 4097053535956 |
| 16 | 29404486634726 |
| 17 | 211035522699946 |
| 18 | 1514598516808216 |
| 19 | 10870248941079889 |
| 20 | 78015599995840787 |
[4,32,220,1578,11303,81105,582032,4177161, 29979239,215160247,1544201029,11082704750, 79540390044,570860083491,4097053535956, 29404486634726,211035522699946,1514598516808216, 10870248941079889,78015599995840787] |