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| n | a(n) |
|---|---|
| 1 | 15 |
| 2 | 56 |
| 3 | 232 |
| 4 | 1008 |
| 5 | 4432 |
| 6 | 19328 |
| 7 | 82944 |
| 8 | 349952 |
| 9 | 1454848 |
| 10 | 5978112 |
| 11 | 24352768 |
| 12 | 98594816 |
| 13 | 397479936 |
| 14 | 1597865984 |
| 15 | 6411452416 |
| 16 | 25695289344 |
| 17 | 102901940224 |
| 18 | 411899002880 |
| 19 | 1648290693120 |
| 20 | 6594803793920 |
| 21 | 26383058206720 |
| 22 | 105541162500096 |
| 23 | 422185252421632 |
[15,56,232,1008,4432,19328,82944,349952,1454848, 5978112,24352768,98594816,397479936,1597865984, 6411452416,25695289344,102901940224,411899002880, 1648290693120,6594803793920,26383058206720, 105541162500096,422185252421632] |