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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 19 |
| 3 | 54 |
| 4 | 124 |
| 5 | 250 |
| 6 | 14795 |
| 7 | 309990 |
| 8 | 2853292 |
| 9 | 14125312 |
| 10 | 46481352 |
| 11 | 116171792 |
| 12 | 240747928 |
| 13 | 438003360 |
| 14 | 725775144 |
| 15 | 1121905200 |
| 16 | 1644235704 |
| 17 | 2310608832 |
| 18 | 3138866760 |
| 19 | 4146851664 |
| 20 | 5352405720 |
| 21 | 6773371104 |
| 22 | 8427589992 |
| 23 | 10332904560 |
[4,19,54,124,250,14795,309990,2853292,14125312, 46481352,116171792,240747928,438003360,725775144, 1121905200,1644235704,2310608832,3138866760, 4146851664,5352405720,6773371104,8427589992, 10332904560] |