The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 26 |
| 3 | 302 |
| 4 | 2416 |
| 5 | 15619 |
| 6 | 88234 |
| 7 | 455192 |
| 8 | 2203488 |
| 9 | 10187685 |
| 10 | 45533450 |
| 11 | 198410786 |
| 12 | 848090912 |
| 13 | 3572085255 |
| 14 | 14875399450 |
| 15 | 61403313100 |
| 16 | 251732291184 |
| 17 | 1026509354985 |
| 18 | 4168403181210 |
| 19 | 16871482830550 |
| 20 | 68111623139600 |
[0,1,26,302,2416,15619,88234,455192,2203488, 10187685,45533450,198410786,848090912,3572085255, 14875399450,61403313100,251732291184, 1026509354985,4168403181210,16871482830550, 68111623139600] |