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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 5 |
| 4 | 17 |
| 5 | 121 |
| 6 | 721 |
| 7 | 6621 |
| 8 | 56545 |
| 9 | 636337 |
| 10 | 7062241 |
| 11 | 94260341 |
| 12 | 1283497841 |
| 13 | 19853570985 |
| 14 | 319471153457 |
| 15 | 5628171840461 |
| 16 | 104260273696961 |
| 17 | 2063430523313761 |
| 18 | 43168502192389825 |
| 19 | 949149114720943077 |
[1,1,1,5,17,121,721,6621,56545,636337,7062241, 94260341,1283497841,19853570985,319471153457, 5628171840461,104260273696961,2063430523313761, 43168502192389825,949149114720943077] |