| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 6 |
| 3 | 28 |
| 4 | 166 |
| 5 | 971 |
| 6 | 5937 |
| 7 | 36736 |
| 8 | 230363 |
| 9 | 1458037 |
| 10 | 9292357 |
| 11 | 59576614 |
| 12 | 383721187 |
| 13 | 2481397399 |
| 14 | 16099317872 |
| 15 | 104753149406 |
| 16 | 683279530195 |
| 17 | 4466548322041 |
| 18 | 29253296829696 |
| 19 | 191917744224242 |
| 20 | 1260998821726319 |
| 21 | 8296736705457073 |
[1,1,6,28,166,971,5937,36736,230363,1458037, 9292357,59576614,383721187,2481397399,16099317872, 104753149406,683279530195,4466548322041, 29253296829696,191917744224242,1260998821726319, 8296736705457073] |