The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 9 |
| 4 | 40 |
| 5 | 264 |
| 6 | 2379 |
| 7 | 27568 |
| 8 | 392895 |
| 9 | 6663624 |
| 10 | 131211423 |
| 11 | 2943137604 |
| 12 | 74087543634 |
| 13 | 2068127523264 |
| 14 | 63395972293650 |
| 15 | 2116776180704988 |
| 16 | 76462961271015326 |
| 17 | 2970720383283042732 |
| 18 | 123517218432709179030 |
| 19 | 5472063213488927240290 |
| 20 | 257315864404023900340860 |
| 21 | 12799687840583182179921204 |
[1,3,9,40,264,2379,27568,392895,6663624,131211423, 2943137604,74087543634,2068127523264, 63395972293650,2116776180704988,76462961271015326, 2970720383283042732,123517218432709179030, 5472063213488927240290,257315864404023900340860, 12799687840583182179921204] |