| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 4 |
| 3 | 175 |
| 4 | 3324 |
| 5 | 42469 |
| 6 | 429120 |
| 7 | 3711027 |
| 8 | 28723640 |
| 9 | 204598130 |
| 10 | 1366223880 |
| 11 | 8664086470 |
| 12 | 52673351080 |
| 13 | 309164754285 |
| 14 | 1761471681568 |
| 15 | 9783594370723 |
| 16 | 53154274959360 |
| 17 | 283267669144390 |
| 18 | 1484104565936920 |
| 19 | 7658877239935362 |
| 20 | 38993558097982312 |
| 21 | 196127054929939810 |
[0,4,175,3324,42469,429120,3711027,28723640, 204598130,1366223880,8664086470,52673351080, 309164754285,1761471681568,9783594370723, 53154274959360,283267669144390,1484104565936920, 7658877239935362,38993558097982312, 196127054929939810] |