The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 15 |
| 4 | 73 |
| 5 | 387 |
| 6 | 2106 |
| 7 | 11998 |
| 8 | 69999 |
| 9 | 418104 |
| 10 | 2540368 |
| 11 | 15660843 |
| 12 | 97692822 |
| 13 | 615559931 |
| 14 | 3911866377 |
| 15 | 25044058215 |
| 16 | 161369414590 |
| 17 | 1045681767924 |
| 18 | 6810222330303 |
| 19 | 44552627690401 |
| 20 | 292642818035352 |
| 21 | 1929238465836366 |
| 22 | 12760620159195044 |
[1,3,15,73,387,2106,11998,69999,418104,2540368, 15660843,97692822,615559931,3911866377, 25044058215,161369414590,1045681767924, 6810222330303,44552627690401,292642818035352, 1929238465836366,12760620159195044] |