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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 6 |
| 3 | 25 |
| 4 | 116 |
| 5 | 517 |
| 6 | 2338 |
| 7 | 10517 |
| 8 | 47400 |
| 9 | 213481 |
| 10 | 961726 |
| 11 | 4332145 |
| 12 | 19515036 |
| 13 | 87908397 |
| 14 | 395998298 |
| 15 | 1783838637 |
| 16 | 8035595600 |
| 17 | 36197658961 |
| 18 | 163058307446 |
| 19 | 734522939465 |
| 20 | 3308779311556 |
| 21 | 14904940203477 |
| 22 | 67141752851858 |
[1,6,25,116,517,2338,10517,47400,213481,961726, 4332145,19515036,87908397,395998298,1783838637, 8035595600,36197658961,163058307446,734522939465, 3308779311556,14904940203477,67141752851858] |