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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 21 |
| 5 | 73 |
| 6 | 240 |
| 7 | 754 |
| 8 | 2309 |
| 9 | 6987 |
| 10 | 21036 |
| 11 | 63202 |
| 12 | 189723 |
| 13 | 569311 |
| 14 | 1708100 |
| 15 | 5124492 |
| 16 | 15373695 |
| 17 | 46121335 |
| 18 | 138364290 |
| 19 | 415093192 |
| 20 | 1245279935 |
| 21 | 3735840201 |
| 22 | 11207521038 |
| 23 | 33622563592 |
| 24 | 100867691301 |
| 25 | 302603074477 |
| 26 | 907809224054 |
[1,2,6,21,73,240,754,2309,6987,21036,63202,189723, 569311,1708100,5124492,15373695,46121335, 138364290,415093192,1245279935,3735840201, 11207521038,33622563592,100867691301,302603074477, 907809224054] |