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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 8 |
| 5 | 42 |
| 6 | 232 |
| 7 | 1277 |
| 8 | 7183 |
| 9 | 41041 |
| 10 | 238315 |
| 11 | 1402076 |
| 12 | 8343804 |
| 13 | 50136483 |
| 14 | 303790544 |
| 15 | 1854115285 |
| 16 | 11388104153 |
| 17 | 70338364135 |
| 18 | 436605050440 |
| 19 | 2722153369473 |
| 20 | 17040017600925 |
| 21 | 107052073186950 |
| 22 | 674752469797923 |
| 23 | 4265733944934540 |
[0,0,1,8,42,232,1277,7183,41041,238315,1402076, 8343804,50136483,303790544,1854115285,11388104153, 70338364135,436605050440,2722153369473, 17040017600925,107052073186950,674752469797923, 4265733944934540] |