| n | a(n) |
|---|---|
| 1 | 6 |
| 2 | 36 |
| 3 | 210 |
| 4 | 1215 |
| 5 | 6960 |
| 6 | 39560 |
| 7 | 223320 |
| 8 | 1253190 |
| 9 | 6995660 |
| 10 | 38870136 |
| 11 | 215074596 |
| 12 | 1185563746 |
| 13 | 6512894520 |
| 14 | 35666937840 |
| 15 | 194765568024 |
| 16 | 1060744346079 |
| 17 | 5762980508994 |
| 18 | 31239002042780 |
| 19 | 168977143019910 |
| 20 | 912220049428041 |
[6,36,210,1215,6960,39560,223320,1253190,6995660, 38870136,215074596,1185563746,6512894520, 35666937840,194765568024,1060744346079, 5762980508994,31239002042780,168977143019910, 912220049428041] |