The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 5 |
| 4 | 18 |
| 5 | 72 |
| 6 | 368 |
| 7 | 1982 |
| 8 | 11514 |
| 9 | 69270 |
| 10 | 430384 |
| 11 | 2736894 |
| 12 | 17752884 |
| 13 | 117039548 |
| 14 | 782480424 |
| 15 | 5294705752 |
| 16 | 36206357114 |
| 17 | 249894328848 |
| 18 | 1739030128872 |
| 19 | 12191512867814 |
| 20 | 86037243899240 |
| 21 | 610827161152012 |
| 22 | 4360291880624504 |
| 23 | 31280354620428378 |
| 24 | 225427088761560916 |
| 25 | 1631398499577667252 |
[1,1,2,5,18,72,368,1982,11514,69270,430384, 2736894,17752884,117039548,782480424,5294705752, 36206357114,249894328848,1739030128872, 12191512867814,86037243899240,610827161152012, 4360291880624504,31280354620428378, 225427088761560916,1631398499577667252] |