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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 5 |
| 4 | 18 |
| 5 | 102 |
| 6 | 848 |
| 7 | 12452 |
| 8 | 265759 |
| 9 | 10454008 |
| 10 | 598047612 |
| 11 | 63620448978 |
| 12 | 9974635937844 |
| 13 | 2905660724913768 |
| 14 | 1268590412128132389 |
| 15 | 1023130650177394611897 |
| 16 | 1258149993547327488275562 |
| 17 | 2834863110716120144290954314 |
| 18 | 9900859865505110360978721901778 |
[1,2,5,18,102,848,12452,265759,10454008,598047612, 63620448978,9974635937844,2905660724913768, 1268590412128132389,1023130650177394611897, 1258149993547327488275562, 2834863110716120144290954314, 9900859865505110360978721901778] |