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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 18 |
| 3 | 160 |
| 4 | 2952 |
| 5 | 17518 |
| 6 | 356398 |
| 7 | 2118905 |
| 8 | 44960137 |
| 9 | 272872198 |
| 10 | 5911110630 |
| 11 | 36457959703 |
| 12 | 799084046960 |
| 13 | 4981910445036 |
| 14 | 110019357014516 |
| 15 | 690925392478349 |
| 16 | 15339905237756384 |
| 17 | 96831631047966404 |
| 18 | 2158535060733668360 |
[0,18,160,2952,17518,356398,2118905,44960137, 272872198,5911110630,36457959703,799084046960, 4981910445036,110019357014516,690925392478349, 15339905237756384,96831631047966404, 2158535060733668360] |