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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 7 |
| 3 | 28 |
| 4 | 171 |
| 5 | 846 |
| 6 | 4942 |
| 7 | 26580 |
| 8 | 153363 |
| 9 | 856900 |
| 10 | 4939682 |
| 11 | 28140476 |
| 12 | 162676878 |
| 13 | 936947116 |
| 14 | 5436375532 |
| 15 | 31526252208 |
| 16 | 183571246659 |
| 17 | 1069552636950 |
| 18 | 6247183319938 |
| 19 | 36524006501180 |
| 20 | 213899020967786 |
| 21 | 1253905101529080 |
| 22 | 7359775341696180 |
| 23 | 43237184121401400 |
[1,1,7,28,171,846,4942,26580,153363,856900, 4939682,28140476,162676878,936947116,5436375532, 31526252208,183571246659,1069552636950, 6247183319938,36524006501180,213899020967786, 1253905101529080,7359775341696180, 43237184121401400] |