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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 30 |
| 3 | 420 |
| 4 | 6930 |
| 5 | 126126 |
| 6 | 2450448 |
| 7 | 49884120 |
| 8 | 1051723530 |
| 9 | 22787343150 |
| 10 | 504636071940 |
| 11 | 11377249621920 |
| 12 | 260363981732400 |
| 13 | 6034149862347600 |
| 14 | 141371511060715200 |
| 15 | 3343436236585914480 |
| 16 | 79726203788589122490 |
| 17 | 1914992149823954412750 |
| 18 | 46295775130831740013500 |
[1,3,30,420,6930,126126,2450448,49884120, 1051723530,22787343150,504636071940, 11377249621920,260363981732400,6034149862347600, 141371511060715200,3343436236585914480, 79726203788589122490,1914992149823954412750, 46295775130831740013500] |