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| n | a(n) |
|---|---|
| 2 | 1 |
| 3 | 2 |
| 4 | 10 |
| 5 | 12 |
| 6 | 84 |
| 7 | 132 |
| 8 | 954 |
| 9 | 1728 |
| 10 | 13290 |
| 11 | 26820 |
| 12 | 217500 |
| 13 | 481320 |
| 14 | 4086600 |
| 15 | 9783480 |
| 16 | 86549820 |
| 17 | 221921280 |
| 18 | 2037627900 |
| 19 | 5552479800 |
| 20 | 52745205240 |
| 21 | 151802154000 |
| 22 | 1487961422640 |
| 23 | 4500041903280 |
| 24 | 45412066438200 |
| 25 | 143712079822080 |
| 26 | 1490217165997560 |
| 27 | 4917227802767280 |
[1,2,10,12,84,132,954,1728,13290,26820,217500, 481320,4086600,9783480,86549820,221921280, 2037627900,5552479800,52745205240,151802154000, 1487961422640,4500041903280,45412066438200, 143712079822080,1490217165997560,4917227802767280] |