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| n | a(n) |
|---|---|
| 0 | 61 |
| 1 | 252 |
| 2 | 16380 |
| 3 | 189280 |
| 4 | 1048572 |
| 5 | 3937752 |
| 6 | 11930464 |
| 7 | 30588480 |
| 8 | 67108860 |
| 9 | 133739676 |
| 10 | 255953880 |
| 11 | 460605600 |
| 12 | 763366240 |
| 13 | 1216356120 |
| 14 | 1928015424 |
| 15 | 2957689280 |
| 16 | 4294967292 |
| 17 | 6082667640 |
| 18 | 8693078940 |
[61,252,16380,189280,1048572,3937752,11930464, 30588480,67108860,133739676,255953880,460605600, 763366240,1216356120,1928015424,2957689280, 4294967292,6082667640,8693078940] |