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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 56 |
| 5 | 7100 |
| 6 | 252792 |
| 7 | 3378942 |
| 8 | 26249184 |
| 9 | 144455454 |
| 10 | 625745100 |
| 11 | 2271361422 |
| 12 | 7192874328 |
| 13 | 20427662398 |
| 14 | 53065637212 |
| 15 | 127956238350 |
| 16 | 289628321664 |
| 17 | 620834113614 |
| 18 | 1269178026012 |
| 19 | 2488676915070 |
| 20 | 4702895069400 |
| 21 | 8598589878606 |
| 22 | 15261688799500 |
| 23 | 26371002575326 |
[0,0,0,56,7100,252792,3378942,26249184,144455454, 625745100,2271361422,7192874328,20427662398, 53065637212,127956238350,289628321664, 620834113614,1269178026012,2488676915070, 4702895069400,8598589878606,15261688799500, 26371002575326] |