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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 15 |
| 3 | 70 |
| 4 | 1596 |
| 5 | 7645 |
| 6 | 175491 |
| 7 | 840826 |
| 8 | 19302360 |
| 9 | 92483161 |
| 10 | 2123084055 |
| 11 | 10172306830 |
| 12 | 233519943636 |
| 13 | 1118861268085 |
| 14 | 25685070715851 |
| 15 | 123064567182466 |
| 16 | 2825124258799920 |
| 17 | 13535983528803121 |
| 18 | 310737983397275295 |
| 19 | 1488835123601160790 |
| 20 | 34178353049441482476 |
[1,15,70,1596,7645,175491,840826,19302360, 92483161,2123084055,10172306830,233519943636, 1118861268085,25685070715851,123064567182466, 2825124258799920,13535983528803121, 310737983397275295,1488835123601160790, 34178353049441482476] |