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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 9 |
| 4 | 33 |
| 5 | 135 |
| 6 | 633 |
| 7 | 3207 |
| 8 | 17589 |
| 9 | 102626 |
| 10 | 636014 |
| 11 | 4160852 |
| 12 | 28676800 |
| 13 | 207267046 |
| 14 | 1566709436 |
| 15 | 12337438198 |
| 16 | 100921477976 |
| 17 | 855109095248 |
| 18 | 7488671736398 |
| 19 | 67655656640892 |
| 20 | 629623562927598 |
| 21 | 6027970886933100 |
| 22 | 59306595225701588 |
| 23 | 599011729235408510 |
| 24 | 6205282969563030610 |
[1,1,3,9,33,135,633,3207,17589,102626,636014, 4160852,28676800,207267046,1566709436,12337438198, 100921477976,855109095248,7488671736398, 67655656640892,629623562927598,6027970886933100, 59306595225701588,599011729235408510, 6205282969563030610] |