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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 4 |
| 2 | 40 |
| 3 | 468 |
| 4 | 5828 |
| 5 | 76260 |
| 6 | 1032444 |
| 7 | 14316584 |
| 8 | 202116108 |
| 9 | 2893451652 |
| 10 | 41886157564 |
| 11 | 611902123284 |
| 12 | 9007199254740 |
| 13 | 133439988963012 |
| 14 | 1987795697598012 |
| 15 | 29752813022112180 |
| 16 | 447193795726343004 |
| 17 | 6746237832670921768 |
| 18 | 102105221251235572188 |
[0,4,40,468,5828,76260,1032444,14316584,202116108, 2893451652,41886157564,611902123284,9007199254740, 133439988963012,1987795697598012, 29752813022112180,447193795726343004, 6746237832670921768,102105221251235572188] |