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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 19 |
| 4 | 130 |
| 5 | 1081 |
| 6 | 10894 |
| 7 | 127639 |
| 8 | 1711210 |
| 9 | 25798141 |
| 10 | 432212134 |
| 11 | 7964801659 |
| 12 | 160121522290 |
| 13 | 3487254825601 |
| 14 | 81790592435374 |
| 15 | 2055350489070079 |
| 16 | 55093108433421370 |
| 17 | 1569052795651631461 |
| 18 | 47315282424232826614 |
| 19 | 1506074331671551028899 |
[1,1,4,19,130,1081,10894,127639,1711210,25798141, 432212134,7964801659,160121522290,3487254825601, 81790592435374,2055350489070079,55093108433421370, 1569052795651631461,47315282424232826614, 1506074331671551028899] |