| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 8 |
| 4 | 41 |
| 5 | 253 |
| 6 | 1858 |
| 7 | 15796 |
| 8 | 152219 |
| 9 | 1638323 |
| 10 | 19467494 |
| 11 | 252998224 |
| 12 | 3568259503 |
| 13 | 54263159347 |
| 14 | 884834059454 |
| 15 | 15397757661092 |
| 16 | 284767413357977 |
| 17 | 5576696746139689 |
| 18 | 115269732256964626 |
| 19 | 2507575465491619672 |
| 20 | 57262481225957071721 |
| 21 | 1369461739453440893261 |
[1,1,2,8,41,253,1858,15796,152219,1638323, 19467494,252998224,3568259503,54263159347, 884834059454,15397757661092,284767413357977, 5576696746139689,115269732256964626, 2507575465491619672,57262481225957071721, 1369461739453440893261] |