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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 56 |
| 3 | 1388 |
| 4 | 50444 |
| 5 | 2436176 |
| 6 | 147308248 |
| 7 | 10720410984 |
| 8 | 913099165080 |
| 9 | 89150817350880 |
| 10 | 9819313409197632 |
| 11 | 1204676163038931744 |
| 12 | 162935364815509750368 |
| 13 | 24088567621306193343360 |
| 14 | 3864931159784777490964608 |
| 15 | 668886871993798772730203136 |
| 16 | 124209455281616641852564586496 |
[1,4,56,1388,50444,2436176,147308248,10720410984, 913099165080,89150817350880,9819313409197632, 1204676163038931744,162935364815509750368, 24088567621306193343360,3864931159784777490964608, 668886871993798772730203136, 124209455281616641852564586496] |