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| n | a(n) |
|---|---|
| 12 | 1 |
| 13 | 2731 |
| 14 | 14913991 |
| 15 | 54301841231 |
| 16 | 237244744338239 |
| 17 | 942314556807454559 |
| 18 | 3920970870875818419999 |
| 19 | 15935828658299317547308959 |
| 20 | 65529064844612576067331339935 |
| 21 | 267883966717492783113707839256735 |
[1,2731,14913991,54301841231,237244744338239, 942314556807454559,3920970870875818419999, 15935828658299317547308959, 65529064844612576067331339935, 267883966717492783113707839256735] |