The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 9 |
| 3 | 20 |
| 4 | 49 |
| 5 | 115 |
| 6 | 343 |
| 7 | 850 |
| 8 | 2401 |
| 9 | 6698 |
| 10 | 18677 |
| 11 | 52383 |
| 12 | 148417 |
| 13 | 418280 |
| 14 | 1184717 |
| 15 | 3357537 |
| 16 | 9518235 |
| 17 | 27001128 |
| 18 | 76637532 |
| 19 | 217530615 |
| 20 | 617624137 |
| 21 | 1753811531 |
| 22 | 4980521844 |
| 23 | 14144892243 |
| 24 | 40174244540 |
| 25 | 114105904403 |
| 26 | 324101321331 |
| 27 | 920579535645 |
| 28 | 2614852152957 |
[1,3,9,20,49,115,343,850,2401,6698,18677,52383, 148417,418280,1184717,3357537,9518235,27001128, 76637532,217530615,617624137,1753811531, 4980521844,14144892243,40174244540,114105904403, 324101321331,920579535645,2614852152957] |