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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 11 |
| 3 | 76 |
| 4 | 520 |
| 5 | 3552 |
| 6 | 24256 |
| 7 | 165632 |
| 8 | 1131008 |
| 9 | 7723008 |
| 10 | 52736000 |
| 11 | 360103936 |
| 12 | 2458943488 |
| 13 | 16790716416 |
| 14 | 114654183424 |
| 15 | 782907736064 |
| 16 | 5346028421120 |
| 17 | 36504965480448 |
| 18 | 249271496474624 |
| 19 | 1702132247953408 |
| 20 | 11622886011830272 |
[2,11,76,520,3552,24256,165632,1131008,7723008, 52736000,360103936,2458943488,16790716416, 114654183424,782907736064,5346028421120, 36504965480448,249271496474624,1702132247953408, 11622886011830272] |