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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 12 |
| 3 | 110 |
| 4 | 1274 |
| 5 | 17136 |
| 6 | 255816 |
| 7 | 4124406 |
| 8 | 70549050 |
| 9 | 1264752060 |
| 10 | 23555382240 |
| 11 | 452806924752 |
| 12 | 8939481277552 |
| 13 | 180551099694400 |
| 14 | 3719061442253520 |
| 15 | 77933728043586630 |
| 16 | 1658001861319441050 |
| 17 | 35749633305661575300 |
| 18 | 780123576993991461000 |
| 19 | 17208112644166765652100 |
[1,2,12,110,1274,17136,255816,4124406,70549050, 1264752060,23555382240,452806924752,8939481277552, 180551099694400,3719061442253520, 77933728043586630,1658001861319441050, 35749633305661575300,780123576993991461000, 17208112644166765652100] |