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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 91 |
| 4 | 240 |
| 5 | 840 |
| 6 | 989 |
| 7 | 5396 |
| 8 | 117719 |
| 9 | 312120 |
| 10 | 1089720 |
| 11 | 1284121 |
| 12 | 7003804 |
| 13 | 152799571 |
| 14 | 405130920 |
| 15 | 1414456320 |
| 16 | 1666787669 |
| 17 | 9090932396 |
| 18 | 198333725039 |
| 19 | 525859622640 |
| 20 | 1835963213040 |
| 21 | 2163489110641 |
| 22 | 11800023246004 |
| 23 | 257437022301451 |
[1,4,91,240,840,989,5396,117719,312120,1089720, 1284121,7003804,152799571,405130920,1414456320, 1666787669,9090932396,198333725039,525859622640, 1835963213040,2163489110641,11800023246004, 257437022301451] |