The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 2 |
| 4 | 4 |
| 5 | 7 |
| 6 | 19 |
| 7 | 42 |
| 8 | 102 |
| 9 | 252 |
| 10 | 532 |
| 11 | 1226 |
| 12 | 3681 |
| 13 | 9100 |
| 14 | 24858 |
| 15 | 61943 |
| 16 | 161857 |
| 17 | 392935 |
| 18 | 1167208 |
| 19 | 3125539 |
| 20 | 8879693 |
| 21 | 23143081 |
| 22 | 63028550 |
| 23 | 161146767 |
| 24 | 480399716 |
| 25 | 1325189141 |
| 26 | 3815350317 |
| 27 | 10255072974 |
[1,2,2,4,7,19,42,102,252,532,1226,3681,9100,24858, 61943,161857,392935,1167208,3125539,8879693, 23143081,63028550,161146767,480399716,1325189141, 3815350317,10255072974] |