| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 13 |
| 4 | 77 |
| 5 | 587 |
| 6 | 5484 |
| 7 | 60582 |
| 8 | 771261 |
| 9 | 11102828 |
| 10 | 178144861 |
| 11 | 3149976426 |
| 12 | 60825085447 |
| 13 | 1273060083700 |
| 14 | 28700081677767 |
| 15 | 693217471426114 |
| 16 | 17857152401368800 |
| 17 | 488620956679818191 |
| 18 | 14152040894854881662 |
| 19 | 432509671322583878614 |
| 20 | 13908794132963653028146 |
[1,1,3,13,77,587,5484,60582,771261,11102828, 178144861,3149976426,60825085447,1273060083700, 28700081677767,693217471426114,17857152401368800, 488620956679818191,14152040894854881662, 432509671322583878614,13908794132963653028146] |