| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 10 |
| 4 | 40 |
| 5 | 155 |
| 6 | 661 |
| 7 | 2809 |
| 8 | 12388 |
| 9 | 55098 |
| 10 | 249064 |
| 11 | 1135248 |
| 12 | 5225124 |
| 13 | 24208799 |
| 14 | 112873953 |
| 15 | 528935624 |
| 16 | 2489987847 |
| 17 | 11767157943 |
| 18 | 55803419262 |
| 19 | 265442664895 |
| 20 | 1266114276385 |
| 21 | 6053949599553 |
| 22 | 29011329072416 |
| 23 | 139305020533736 |
| 24 | 670130501757298 |
| 25 | 3229062672948896 |
| 26 | 15583269734938239 |
| 27 | 75310011395231900 |
[1,1,3,10,40,155,661,2809,12388,55098,249064, 1135248,5225124,24208799,112873953,528935624, 2489987847,11767157943,55803419262,265442664895, 1266114276385,6053949599553,29011329072416, 139305020533736,670130501757298,3229062672948896, 15583269734938239,75310011395231900] |