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| n | a(n) |
|---|---|
| 1 | 10 |
| 2 | 60 |
| 3 | 336 |
| 4 | 1776 |
| 5 | 8914 |
| 6 | 43202 |
| 7 | 203560 |
| 8 | 939730 |
| 9 | 4266332 |
| 10 | 19120668 |
| 11 | 84774066 |
| 12 | 372587962 |
| 13 | 1625370614 |
| 14 | 7046239064 |
| 15 | 30380655534 |
| 16 | 130376624746 |
| 17 | 557189663232 |
| 18 | 2372600434880 |
| 19 | 10070044493366 |
| 20 | 42616195500252 |
| 21 | 179877106083440 |
[10,60,336,1776,8914,43202,203560,939730,4266332, 19120668,84774066,372587962,1625370614,7046239064, 30380655534,130376624746,557189663232, 2372600434880,10070044493366,42616195500252, 179877106083440] |