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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 40 |
| 3 | 1088 |
| 4 | 21888 |
| 5 | 397312 |
| 6 | 6883328 |
| 7 | 116244480 |
| 8 | 1932230656 |
| 9 | 31778668544 |
| 10 | 518791888896 |
| 11 | 8424565768192 |
| 12 | 136279337467904 |
| 13 | 2198302774788096 |
| 14 | 35386835907641344 |
| 15 | 568757233463066624 |
| 16 | 9130929873047519232 |
| 17 | 146464646890277306368 |
| 18 | 2347871574175904694272 |
[0,40,1088,21888,397312,6883328,116244480, 1932230656,31778668544,518791888896,8424565768192, 136279337467904,2198302774788096, 35386835907641344,568757233463066624, 9130929873047519232,146464646890277306368, 2347871574175904694272] |