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| n | a(n) |
|---|---|
| 4 | 15 |
| 5 | 144 |
| 6 | 848 |
| 7 | 3936 |
| 8 | 15800 |
| 9 | 57420 |
| 10 | 194034 |
| 11 | 619912 |
| 12 | 1894152 |
| 13 | 5579536 |
| 14 | 15939998 |
| 15 | 44363268 |
| 16 | 120707904 |
| 17 | 321973720 |
| 18 | 843826794 |
| 19 | 2176829360 |
| 20 | 5535969328 |
| 21 | 13896678404 |
| 22 | 34470255256 |
| 23 | 84565452840 |
| 24 | 205353216490 |
| 25 | 493934650180 |
| 26 | 1177496577964 |
| 27 | 2783578273632 |
| 28 | 6528396084669 |
[15,144,848,3936,15800,57420,194034,619912, 1894152,5579536,15939998,44363268,120707904, 321973720,843826794,2176829360,5535969328, 13896678404,34470255256,84565452840,205353216490, 493934650180,1177496577964,2783578273632, 6528396084669] |