The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 9 |
| 2 | 18 |
| 3 | 54 |
| 4 | 144 |
| 5 | 396 |
| 6 | 1080 |
| 7 | 2952 |
| 8 | 8064 |
| 9 | 22032 |
| 10 | 60192 |
| 11 | 164448 |
| 12 | 449280 |
| 13 | 1227456 |
| 14 | 3353472 |
| 15 | 9161856 |
| 16 | 25030656 |
| 17 | 68385024 |
| 18 | 186831360 |
| 19 | 510432768 |
| 20 | 1394528256 |
| 21 | 3809922048 |
| 22 | 10408900608 |
| 23 | 28437645312 |
| 24 | 77693091840 |
| 25 | 212261474304 |
[9,18,54,144,396,1080,2952,8064,22032,60192, 164448,449280,1227456,3353472,9161856,25030656, 68385024,186831360,510432768,1394528256, 3809922048,10408900608,28437645312,77693091840, 212261474304] |