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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 8 |
| 3 | 66 |
| 4 | 600 |
| 5 | 5164 |
| 6 | 41768 |
| 7 | 317584 |
| 8 | 2280792 |
| 9 | 15573120 |
| 10 | 101743312 |
| 11 | 639664960 |
| 12 | 3889101336 |
| 13 | 22961959168 |
| 14 | 132118984560 |
| 15 | 743046249664 |
| 16 | 4095077270128 |
| 17 | 22163717040384 |
| 18 | 118021533366432 |
| 19 | 619313064407680 |
| 20 | 3206924122635928 |
[0,8,66,600,5164,41768,317584,2280792,15573120, 101743312,639664960,3889101336,22961959168, 132118984560,743046249664,4095077270128, 22163717040384,118021533366432,619313064407680, 3206924122635928] |