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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 25 |
| 4 | 197 |
| 5 | 1797 |
| 6 | 18178 |
| 7 | 198937 |
| 8 | 2318858 |
| 9 | 28487593 |
| 10 | 366129764 |
| 11 | 4896068759 |
| 12 | 67843403960 |
| 13 | 971032668429 |
| 14 | 14319735032679 |
| 15 | 217136949146091 |
| 16 | 3379973833321141 |
| 17 | 53936100582832901 |
| 18 | 881318215466710693 |
| 19 | 14731508761600217914 |
[1,1,4,25,197,1797,18178,198937,2318858,28487593, 366129764,4896068759,67843403960,971032668429, 14319735032679,217136949146091,3379973833321141, 53936100582832901,881318215466710693, 14731508761600217914] |