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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 30 |
| 5 | 260 |
| 6 | 2358 |
| 7 | 20430 |
| 8 | 176774 |
| 9 | 1527918 |
| 10 | 13204026 |
| 11 | 114099558 |
| 12 | 985963206 |
| 13 | 8519922122 |
| 14 | 73622499446 |
| 15 | 636187953758 |
| 16 | 5497437822074 |
| 17 | 47504550336526 |
| 18 | 410497104019406 |
| 19 | 3547194348471034 |
| 20 | 30652074338152030 |
| 21 | 264871210587660230 |
[0,0,0,30,260,2358,20430,176774,1527918,13204026, 114099558,985963206,8519922122,73622499446, 636187953758,5497437822074,47504550336526, 410497104019406,3547194348471034, 30652074338152030,264871210587660230] |