The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 18 |
| 3 | 61 |
| 4 | 225 |
| 5 | 716 |
| 6 | 2272 |
| 7 | 6826 |
| 8 | 20238 |
| 9 | 58552 |
| 10 | 167625 |
| 11 | 473929 |
| 12 | 1330490 |
| 13 | 3709591 |
| 14 | 10296336 |
| 15 | 28466065 |
| 16 | 78481065 |
| 17 | 215878221 |
| 18 | 592832960 |
| 19 | 1625887129 |
| 20 | 4454936029 |
| 21 | 12198071235 |
| 22 | 33383810793 |
| 23 | 91336813784 |
| 24 | 249851178964 |
| 25 | 683421422654 |
[1,3,18,61,225,716,2272,6826,20238,58552,167625, 473929,1330490,3709591,10296336,28466065,78481065, 215878221,592832960,1625887129,4454936029, 12198071235,33383810793,91336813784,249851178964, 683421422654] |