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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 260 |
| 3 | 9855 |
| 4 | 131104 |
| 5 | 976625 |
| 6 | 5038956 |
| 7 | 20176975 |
| 8 | 67109120 |
| 9 | 193710609 |
| 10 | 500000500 |
| 11 | 1178974511 |
| 12 | 2579891040 |
| 13 | 5302250785 |
| 14 | 10330524764 |
| 15 | 19221681375 |
| 16 | 34359740416 |
| 17 | 59293940705 |
| 18 | 99179648100 |
| 19 | 161343852319 |
| 20 | 256000004000 |
[0,1,260,9855,131104,976625,5038956,20176975, 67109120,193710609,500000500,1178974511, 2579891040,5302250785,10330524764,19221681375, 34359740416,59293940705,99179648100,161343852319, 256000004000] |