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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 6 |
| 3 | 63 |
| 4 | 837 |
| 5 | 12672 |
| 6 | 208686 |
| 7 | 3647568 |
| 8 | 66697203 |
| 9 | 1264307667 |
| 10 | 24696153573 |
| 11 | 495076265421 |
| 12 | 10157438738790 |
| 13 | 212900154037875 |
| 14 | 4553735135491134 |
| 15 | 99341289091151409 |
| 16 | 2210262851488661562 |
| 17 | 50173932628981325523 |
| 18 | 1162965513498859292415 |
| 19 | 27554435907912281877315 |
| 20 | 668277970101220006626558 |
| 21 | 16617278354076763108026795 |
[1,1,6,63,837,12672,208686,3647568,66697203, 1264307667,24696153573,495076265421, 10157438738790,212900154037875,4553735135491134, 99341289091151409,2210262851488661562, 50173932628981325523,1162965513498859292415, 27554435907912281877315,668277970101220006626558, 16617278354076763108026795] |