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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 4 |
| 2 | 125 |
| 3 | 1078 |
| 4 | 5220 |
| 5 | 18150 |
| 6 | 50869 |
| 7 | 122500 |
| 8 | 263568 |
| 9 | 519840 |
| 10 | 956725 |
| 11 | 1664234 |
| 12 | 2762500 |
| 13 | 4407858 |
| 14 | 6799485 |
| 15 | 10186600 |
| 16 | 14876224 |
| 17 | 21241500 |
| 18 | 29730573 |
| 19 | 40876030 |
| 20 | 55304900 |
| 21 | 73749214 |
| 22 | 97057125 |
| 23 | 126204588 |
| 24 | 162307600 |
| 25 | 206635000 |
| 26 | 260621829 |
[0,4,125,1078,5220,18150,50869,122500,263568, 519840,956725,1664234,2762500,4407858,6799485, 10186600,14876224,21241500,29730573,40876030, 55304900,73749214,97057125,126204588,162307600, 206635000,260621829] |