The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 13 |
| 4 | 48 |
| 5 | 174 |
| 6 | 664 |
| 7 | 2513 |
| 8 | 9730 |
| 9 | 37582 |
| 10 | 147038 |
| 11 | 574446 |
| 12 | 2260814 |
| 13 | 8893738 |
| 14 | 35148964 |
| 15 | 138890385 |
| 16 | 550442708 |
| 17 | 2181637152 |
| 18 | 8663905570 |
| 19 | 34411664264 |
| 20 | 136862355144 |
| 21 | 544428822504 |
| 22 | 2167767306078 |
| 23 | 8633032307046 |
| 24 | 34404130526250 |
| 25 | 137130510324094 |
| 26 | 546859386049220 |
| 27 | 2181154062631162 |
[1,1,4,13,48,174,664,2513,9730,37582,147038, 574446,2260814,8893738,35148964,138890385, 550442708,2181637152,8663905570,34411664264, 136862355144,544428822504,2167767306078, 8633032307046,34404130526250,137130510324094, 546859386049220,2181154062631162] |