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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 6 |
| 2 | 52 |
| 3 | 411 |
| 4 | 3392 |
| 5 | 30070 |
| 6 | 287802 |
| 7 | 2969267 |
| 8 | 32902560 |
| 9 | 389989449 |
| 10 | 4924511300 |
| 11 | 65995764461 |
| 12 | 935412316380 |
| 13 | 13978234748257 |
| 14 | 219593721606826 |
| 15 | 3617245945896600 |
| 16 | 62330776215811680 |
| 17 | 1121143456571006754 |
| 18 | 21008889235589947362 |
[0,6,52,411,3392,30070,287802,2969267,32902560, 389989449,4924511300,65995764461,935412316380, 13978234748257,219593721606826,3617245945896600, 62330776215811680,1121143456571006754, 21008889235589947362] |