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| n | a(n) |
|---|---|
| 1 | 20 |
| 2 | 300 |
| 3 | 2040 |
| 4 | 8840 |
| 5 | 28860 |
| 6 | 77700 |
| 7 | 182000 |
| 8 | 383760 |
| 9 | 745380 |
| 10 | 1355420 |
| 11 | 2335080 |
| 12 | 3845400 |
| 13 | 6095180 |
| 14 | 9349620 |
| 15 | 13939680 |
| 16 | 20272160 |
| 17 | 28840500 |
| 18 | 40236300 |
| 19 | 55161560 |
| 20 | 74441640 |
| 21 | 99038940 |
| 22 | 130067300 |
| 23 | 168807120 |
| 24 | 216721200 |
| 25 | 275471300 |
| 26 | 346935420 |
[20,300,2040,8840,28860,77700,182000,383760, 745380,1355420,2335080,3845400,6095180,9349620, 13939680,20272160,28840500,40236300,55161560, 74441640,99038940,130067300,168807120,216721200, 275471300,346935420] |