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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 28 |
| 4 | 332 |
| 5 | 5748 |
| 6 | 131940 |
| 7 | 3791692 |
| 8 | 131375324 |
| 9 | 5343640212 |
| 10 | 250142552212 |
| 11 | 13271217848604 |
| 12 | 788346022938556 |
| 13 | 51916178572447140 |
| 14 | 3759254932421361284 |
| 15 | 297243198474965188732 |
| 16 | 25513664852425377663756 |
| 17 | 2365246919693613357168916 |
| 18 | 235776253411115081902083556 |
| 19 | 25174157913006507920211300588 |
| 20 | 2869108641038261410331666767772 |
[1,4,28,332,5748,131940,3791692,131375324, 5343640212,250142552212,13271217848604, 788346022938556,51916178572447140, 3759254932421361284,297243198474965188732, 25513664852425377663756,2365246919693613357168916, 235776253411115081902083556, 25174157913006507920211300588, 2869108641038261410331666767772] |