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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 15 |
| 4 | 148 |
| 5 | 2565 |
| 6 | 59046 |
| 7 | 1825831 |
| 8 | 70678280 |
| 9 | 3343670217 |
| 10 | 188213143690 |
| 11 | 12380664239691 |
| 12 | 937445644041996 |
| 13 | 80731184378264173 |
| 14 | 7828455595505947598 |
| 15 | 847603141493494555695 |
| 16 | 101732530008690207859216 |
| 17 | 13451340197177805355768209 |
| 18 | 1948644186311260903900163346 |
| 19 | 307791516722206533702105826963 |
| 20 | 52778747788778673408416550382100 |
[1,1,2,15,148,2565,59046,1825831,70678280, 3343670217,188213143690,12380664239691, 937445644041996,80731184378264173, 7828455595505947598,847603141493494555695, 101732530008690207859216, 13451340197177805355768209, 1948644186311260903900163346, 307791516722206533702105826963, 52778747788778673408416550382100] |