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| n | a(n) |
|---|---|
| 0 | 3 |
| 1 | 3 |
| 2 | 21 |
| 3 | 84 |
| 4 | 381 |
| 5 | 1668 |
| 6 | 7374 |
| 7 | 32511 |
| 8 | 143445 |
| 9 | 632775 |
| 10 | 2791506 |
| 11 | 12314613 |
| 12 | 54325650 |
| 13 | 239656134 |
| 14 | 1057236915 |
| 15 | 4663973199 |
| 16 | 20574997221 |
| 17 | 90766067772 |
| 18 | 400412159841 |
| 19 | 1766407883376 |
| 20 | 7792462676946 |
| 21 | 34376247490935 |
| 22 | 151649926417857 |
| 23 | 668999726876127 |
| 24 | 2951274986626458 |
[3,3,21,84,381,1668,7374,32511,143445,632775, 2791506,12314613,54325650,239656134,1057236915, 4663973199,20574997221,90766067772,400412159841, 1766407883376,7792462676946,34376247490935, 151649926417857,668999726876127,2951274986626458] |