| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 18 |
| 4 | 153 |
| 5 | 1638 |
| 6 | 20898 |
| 7 | 307908 |
| 8 | 5134293 |
| 9 | 95518278 |
| 10 | 1961333838 |
| 11 | 44069970348 |
| 12 | 1075902476058 |
| 13 | 28367410077468 |
| 14 | 803551902237828 |
| 15 | 24342558819042888 |
| 16 | 785445178323709773 |
| 17 | 26896354975287884358 |
| 18 | 974297972094661642518 |
| 19 | 37225733779871789177628 |
| 20 | 1496237868417003741147438 |
[1,3,18,153,1638,20898,307908,5134293,95518278, 1961333838,44069970348,1075902476058, 28367410077468,803551902237828,24342558819042888, 785445178323709773,26896354975287884358, 974297972094661642518,37225733779871789177628, 1496237868417003741147438] |