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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 4 |
| 3 | 4 |
| 4 | 24 |
| 5 | 78 |
| 6 | 1908 |
| 7 | 23368 |
| 8 | 1961200 |
| 9 | 75942758 |
| 10 | 25703384940 |
| 11 | 4184912454930 |
| 12 | 4462909435830552 |
| 13 | 2245354417775573206 |
| 14 | 10567193418810168583576 |
| 15 | 24001585002447984453495392 |
| 16 | 348615956932626441906675011568 |
| 17 | 2412972383955442904868321667433106 |
| 18 | 162906453913051798826796439651249753404 |
[2,4,4,24,78,1908,23368,1961200,75942758, 25703384940,4184912454930,4462909435830552, 2245354417775573206,10567193418810168583576, 24001585002447984453495392, 348615956932626441906675011568, 2412972383955442904868321667433106, 162906453913051798826796439651249753404] |