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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 19 |
| 5 | 132 |
| 6 | 991 |
| 7 | 7740 |
| 8 | 62020 |
| 9 | 505857 |
| 10 | 4180132 |
| 11 | 34889514 |
| 12 | 293518072 |
| 13 | 2485191753 |
| 14 | 21153817090 |
| 15 | 180865139538 |
| 16 | 1552289627872 |
| 17 | 13366436688402 |
| 18 | 115425148203235 |
| 19 | 999256943147094 |
| 20 | 8670047414816233 |
| 21 | 75375298322580081 |
| 22 | 656465004512563546 |
[1,0,1,3,19,132,991,7740,62020,505857,4180132, 34889514,293518072,2485191753,21153817090, 180865139538,1552289627872,13366436688402, 115425148203235,999256943147094,8670047414816233, 75375298322580081,656465004512563546] |