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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 7 |
| 4 | 28 |
| 5 | 133 |
| 6 | 700 |
| 7 | 4039 |
| 8 | 25160 |
| 9 | 167637 |
| 10 | 1186482 |
| 11 | 8872752 |
| 12 | 69810994 |
| 13 | 575912978 |
| 14 | 4967058182 |
| 15 | 44675926159 |
| 16 | 418157494016 |
| 17 | 4065044047125 |
| 18 | 40973402647058 |
| 19 | 427535487044903 |
| 20 | 4611642948647118 |
| 21 | 51354908876927025 |
[1,1,2,7,28,133,700,4039,25160,167637,1186482, 8872752,69810994,575912978,4967058182,44675926159, 418157494016,4065044047125,40973402647058, 427535487044903,4611642948647118, 51354908876927025] |