The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 9 |
| 5 | 21 |
| 6 | 51 |
| 7 | 127 |
| 8 | 323 |
| 9 | 835 |
| 10 | 2188 |
| 11 | 5798 |
| 12 | 15511 |
| 13 | 41835 |
| 14 | 113633 |
| 15 | 310557 |
| 16 | 853333 |
| 17 | 2355861 |
| 18 | 6531062 |
| 19 | 18171848 |
| 20 | 50722229 |
| 21 | 141973073 |
| 22 | 398351055 |
| 23 | 1120056347 |
| 24 | 3155043447 |
| 25 | 8901325751 |
| 26 | 25147423616 |
| 27 | 71127785002 |
| 28 | 201381834019 |
| 29 | 570655858439 |
| 30 | 1618256772285 |
[1,1,2,4,9,21,51,127,323,835,2188,5798,15511, 41835,113633,310557,853333,2355861,6531062, 18171848,50722229,141973073,398351055,1120056347, 3155043447,8901325751,25147423616,71127785002, 201381834019,570655858439,1618256772285] |