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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 28 |
| 2 | 756 |
| 3 | 20034 |
| 4 | 530712 |
| 5 | 14054040 |
| 6 | 372171618 |
| 7 | 9855587196 |
| 8 | 260988761124 |
| 9 | 6911320818402 |
| 10 | 183020737961880 |
| 11 | 4846626473132808 |
| 12 | 128344953881202786 |
| 13 | 3398740810188105564 |
| 14 | 90003063973732401492 |
| 15 | 2383397845569631005570 |
[1,28,756,20034,530712,14054040,372171618, 9855587196,260988761124,6911320818402, 183020737961880,4846626473132808, 128344953881202786,3398740810188105564, 90003063973732401492,2383397845569631005570] |