| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 12 |
| 3 | 72 |
| 4 | 428 |
| 5 | 2294 |
| 6 | 11932 |
| 7 | 60304 |
| 8 | 297092 |
| 9 | 1443498 |
| 10 | 6930508 |
| 11 | 32917852 |
| 12 | 155025096 |
| 13 | 724982468 |
| 14 | 3370079700 |
| 15 | 15584464186 |
| 16 | 71742003424 |
| 17 | 328950577598 |
| 18 | 1503015006696 |
| 19 | 6845967619642 |
| 20 | 31094637435220 |
| 21 | 140875688981220 |
| 22 | 636779907204164 |
[2,12,72,428,2294,11932,60304,297092,1443498, 6930508,32917852,155025096,724982468,3370079700, 15584464186,71742003424,328950577598, 1503015006696,6845967619642,31094637435220, 140875688981220,636779907204164] |