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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 24 |
| 3 | 108 |
| 4 | 512 |
| 5 | 2164 |
| 6 | 9464 |
| 7 | 39004 |
| 8 | 163008 |
| 9 | 663588 |
| 10 | 2713752 |
| 11 | 10954764 |
| 12 | 44328512 |
| 13 | 178160724 |
| 14 | 716821752 |
| 15 | 2874497660 |
| 16 | 11532111232 |
| 17 | 46187508676 |
| 18 | 185028540696 |
| 19 | 740595436652 |
| 20 | 2964628293504 |
| 21 | 11862432443764 |
| 22 | 47467812675320 |
| 23 | 189902835709212 |
| 24 | 759756868215872 |
[1,4,24,108,512,2164,9464,39004,163008,663588, 2713752,10954764,44328512,178160724,716821752, 2874497660,11532111232,46187508676,185028540696, 740595436652,2964628293504,11862432443764, 47467812675320,189902835709212,759756868215872] |