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| n | a(n) |
|---|---|
| 1 | 120 |
| 2 | 420 |
| 3 | 1328 |
| 4 | 4652 |
| 5 | 14944 |
| 6 | 52468 |
| 7 | 170864 |
| 8 | 601100 |
| 9 | 1980544 |
| 10 | 6979348 |
| 11 | 23223440 |
| 12 | 81953324 |
| 13 | 274931488 |
| 14 | 971325748 |
| 15 | 3280518320 |
| 16 | 11600884556 |
| 17 | 39397352128 |
| 18 | 139427487316 |
| 19 | 475663660496 |
| 20 | 1684432450412 |
| 21 | 5768254899040 |
| 22 | 20437259824756 |
[120,420,1328,4652,14944,52468,170864,601100, 1980544,6979348,23223440,81953324,274931488, 971325748,3280518320,11600884556,39397352128, 139427487316,475663660496,1684432450412, 5768254899040,20437259824756] |