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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 6 |
| 3 | 30 |
| 4 | 219 |
| 5 | 2013 |
| 6 | 17443 |
| 7 | 158594 |
| 8 | 1441287 |
| 9 | 13145287 |
| 10 | 120045930 |
| 11 | 1096641326 |
| 12 | 10020505046 |
| 13 | 91567796475 |
| 14 | 836780632957 |
| 15 | 7646916779234 |
| 16 | 69881717942041 |
| 17 | 638619004480617 |
| 18 | 5836070553261507 |
| 19 | 53333416849369472 |
| 20 | 487391957394071310 |
[0,6,30,219,2013,17443,158594,1441287,13145287, 120045930,1096641326,10020505046,91567796475, 836780632957,7646916779234,69881717942041, 638619004480617,5836070553261507, 53333416849369472,487391957394071310] |