The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 4 |
| 4 | 14 |
| 5 | 47 |
| 6 | 164 |
| 7 | 565 |
| 8 | 1982 |
| 9 | 6977 |
| 10 | 24850 |
| 11 | 89082 |
| 12 | 321855 |
| 13 | 1169853 |
| 14 | 4276923 |
| 15 | 15713799 |
| 16 | 57998270 |
| 17 | 214934984 |
| 18 | 799473752 |
| 19 | 2983682702 |
| 20 | 11169374372 |
| 21 | 41929478873 |
| 22 | 157807392886 |
| 23 | 595340271682 |
| 24 | 2250901007539 |
| 25 | 8527699269192 |
| 26 | 32369066434276 |
[0,0,1,4,14,47,164,565,1982,6977,24850,89082, 321855,1169853,4276923,15713799,57998270, 214934984,799473752,2983682702,11169374372, 41929478873,157807392886,595340271682, 2250901007539,8527699269192,32369066434276] |