| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 20 |
| 2 | 268 |
| 3 | 3116 |
| 4 | 41308 |
| 5 | 559340 |
| 6 | 7702750 |
| 7 | 106934246 |
| 8 | 1491033780 |
| 9 | 20837241344 |
| 10 | 291544100378 |
| 11 | 4081622919042 |
| 12 | 57160810856050 |
| 13 | 800635091767934 |
| 14 | 11215210012054526 |
| 15 | 157108281806511326 |
| 16 | 2200900956018966740 |
[1,20,268,3116,41308,559340,7702750,106934246, 1491033780,20837241344,291544100378,4081622919042, 57160810856050,800635091767934,11215210012054526, 157108281806511326,2200900956018966740] |