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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 20 |
| 3 | 210 |
| 4 | 1309 |
| 5 | 5720 |
| 6 | 19536 |
| 7 | 55825 |
| 8 | 139490 |
| 9 | 314019 |
| 10 | 650440 |
| 11 | 1258796 |
| 12 | 2302455 |
| 13 | 4015570 |
| 14 | 6724004 |
| 15 | 10870035 |
| 16 | 17041156 |
| 17 | 26003285 |
| 18 | 38738700 |
| 19 | 56489014 |
| 20 | 80803505 |
| 21 | 113593116 |
| 22 | 157190440 |
| 23 | 214416005 |
| 24 | 288651174 |
| 25 | 383917975 |
| 26 | 504966176 |
| 27 | 657367920 |
[1,20,210,1309,5720,19536,55825,139490,314019, 650440,1258796,2302455,4015570,6724004,10870035, 17041156,26003285,38738700,56489014,80803505, 113593116,157190440,214416005,288651174,383917975, 504966176,657367920] |