| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 6 |
| 3 | 30 |
| 4 | 144 |
| 5 | 685 |
| 6 | 3258 |
| 7 | 15533 |
| 8 | 74280 |
| 9 | 356283 |
| 10 | 1713690 |
| 11 | 8263596 |
| 12 | 39938616 |
| 13 | 193419915 |
| 14 | 938430990 |
| 15 | 4560542550 |
| 16 | 22195961280 |
| 17 | 108171753355 |
| 18 | 527816696850 |
| 19 | 2578310320610 |
| 20 | 12607504827600 |
| 21 | 61706212037295 |
| 22 | 302275142049870 |
| 23 | 1481908332595625 |
| 24 | 7270432009471224 |
[1,6,30,144,685,3258,15533,74280,356283,1713690, 8263596,39938616,193419915,938430990,4560542550, 22195961280,108171753355,527816696850, 2578310320610,12607504827600,61706212037295, 302275142049870,1481908332595625,7270432009471224] |