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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 25 |
| 3 | 253 |
| 4 | 2065 |
| 5 | 15541 |
| 6 | 112825 |
| 7 | 804973 |
| 8 | 5692705 |
| 9 | 40071781 |
| 10 | 281367625 |
| 11 | 1972955293 |
| 12 | 13823978545 |
| 13 | 96820307221 |
| 14 | 677949854425 |
| 15 | 4746473419213 |
| 16 | 33228592555585 |
| 17 | 232613204977861 |
| 18 | 1628344491013225 |
| 19 | 11398619145204733 |
[0,1,25,253,2065,15541,112825,804973,5692705, 40071781,281367625,1972955293,13823978545, 96820307221,677949854425,4746473419213, 33228592555585,232613204977861,1628344491013225, 11398619145204733] |