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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 78 |
| 3 | 1692 |
| 4 | 25740 |
| 5 | 302850 |
| 6 | 2912910 |
| 7 | 23744840 |
| 8 | 168278760 |
| 9 | 1056789450 |
| 10 | 5968878630 |
| 11 | 30684132468 |
| 12 | 144977296932 |
| 13 | 634756203018 |
| 14 | 2593322651430 |
| 15 | 9946019437200 |
| 16 | 35995371261360 |
| 17 | 123490242018990 |
| 18 | 403237594259010 |
| 19 | 1257743358034100 |
| 20 | 3759426449644740 |
| 21 | 10799525727846702 |
[2,78,1692,25740,302850,2912910,23744840, 168278760,1056789450,5968878630,30684132468, 144977296932,634756203018,2593322651430, 9946019437200,35995371261360,123490242018990, 403237594259010,1257743358034100,3759426449644740, 10799525727846702] |