| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 24 |
| 3 | 230 |
| 4 | 852 |
| 5 | 3780 |
| 6 | 28540 |
| 7 | 187564 |
| 8 | 1003470 |
| 9 | 5652212 |
| 10 | 35138340 |
| 11 | 212926852 |
| 12 | 1237635874 |
| 13 | 7275468358 |
| 14 | 43582711216 |
| 15 | 259742505976 |
| 16 | 1535394584256 |
| 17 | 9097251626562 |
| 18 | 54097987358160 |
| 19 | 321364448756760 |
| 20 | 1905998980152644 |
[1,24,230,852,3780,28540,187564,1003470,5652212, 35138340,212926852,1237635874,7275468358, 43582711216,259742505976,1535394584256, 9097251626562,54097987358160,321364448756760, 1905998980152644] |