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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 24 |
| 3 | 280 |
| 4 | 4161 |
| 5 | 74187 |
| 6 | 1533088 |
| 7 | 35893920 |
| 8 | 936693681 |
| 9 | 26911176067 |
| 10 | 842965594392 |
| 11 | 28564004820888 |
| 12 | 1040256607904209 |
| 13 | 40494874311730731 |
| 14 | 1677141926085541632 |
| 15 | 73603066948190278912 |
| 16 | 3410716757745670379553 |
| 17 | 166367131440489068335299 |
| 18 | 8518446121149783644274136 |
[1,3,24,280,4161,74187,1533088,35893920,936693681, 26911176067,842965594392,28564004820888, 1040256607904209,40494874311730731, 1677141926085541632,73603066948190278912, 3410716757745670379553,166367131440489068335299, 8518446121149783644274136] |