| n | a(n) |
|---|---|
| 1 | 20 |
| 2 | 181 |
| 3 | 2234 |
| 4 | 18564 |
| 5 | 140884 |
| 6 | 1052190 |
| 7 | 7579137 |
| 8 | 51585784 |
| 9 | 331270888 |
| 10 | 2024909124 |
| 11 | 11885134942 |
| 12 | 67329174131 |
| 13 | 369027185265 |
| 14 | 1959956349517 |
| 15 | 10103702621330 |
| 16 | 50645615019582 |
| 17 | 247273236084923 |
| 18 | 1177685989979054 |
| 19 | 5478135751536604 |
[20,181,2234,18564,140884,1052190,7579137, 51585784,331270888,2024909124,11885134942, 67329174131,369027185265,1959956349517, 10103702621330,50645615019582,247273236084923, 1177685989979054,5478135751536604] |