The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 6 |
| 4 | 60 |
| 5 | 522 |
| 6 | 4452 |
| 7 | 38130 |
| 8 | 329832 |
| 9 | 2884056 |
| 10 | 25476936 |
| 11 | 227145654 |
| 12 | 2041930920 |
| 13 | 18490834362 |
| 14 | 168537705300 |
| 15 | 1545096559812 |
| 16 | 14238592913328 |
| 17 | 131826509242650 |
| 18 | 1225645805016864 |
| 19 | 11438847800351118 |
| 20 | 107128560124123524 |
| 21 | 1006475582377759578 |
| 22 | 9483340466106708180 |
| 23 | 89593844489912910294 |
[0,0,6,60,522,4452,38130,329832,2884056,25476936, 227145654,2041930920,18490834362,168537705300, 1545096559812,14238592913328,131826509242650, 1225645805016864,11438847800351118, 107128560124123524,1006475582377759578, 9483340466106708180,89593844489912910294] |