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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 9 |
| 5 | 21 |
| 6 | 81 |
| 7 | 351 |
| 8 | 1233 |
| 9 | 10249 |
| 10 | 75841 |
| 11 | 388411 |
| 12 | 3733401 |
| 13 | 33702813 |
| 14 | 215375889 |
| 15 | 1984583511 |
| 16 | 19181083041 |
| 17 | 141963117201 |
| 18 | 1797976123393 |
| 19 | 22534941675379 |
| 20 | 202605151063081 |
| 21 | 2992764505338021 |
| 22 | 43182110678814801 |
| 23 | 445326641624332623 |
[1,1,1,3,9,21,81,351,1233,10249,75841,388411, 3733401,33702813,215375889,1984583511,19181083041, 141963117201,1797976123393,22534941675379, 202605151063081,2992764505338021, 43182110678814801,445326641624332623] |