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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 13 |
| 4 | 66 |
| 5 | 406 |
| 6 | 2602 |
| 7 | 17271 |
| 8 | 118444 |
| 9 | 829514 |
| 10 | 5914980 |
| 11 | 42791085 |
| 12 | 313277294 |
| 13 | 2316793170 |
| 14 | 17281455882 |
| 15 | 129867946828 |
| 16 | 982293317064 |
| 17 | 7472406051744 |
| 18 | 57132051350160 |
| 19 | 438797394096378 |
| 20 | 3383870656327576 |
| 21 | 26191385476141936 |
[1,1,2,13,66,406,2602,17271,118444,829514,5914980, 42791085,313277294,2316793170,17281455882, 129867946828,982293317064,7472406051744, 57132051350160,438797394096378,3383870656327576, 26191385476141936] |