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| n | a(n) |
|---|---|
| 1 | 56 |
| 2 | 240 |
| 3 | 916 |
| 4 | 3800 |
| 5 | 14828 |
| 6 | 60552 |
| 7 | 239044 |
| 8 | 967784 |
| 9 | 3845148 |
| 10 | 15493000 |
| 11 | 61775668 |
| 12 | 248247480 |
| 13 | 991807292 |
| 14 | 3979719864 |
| 15 | 15917452772 |
| 16 | 63817779896 |
| 17 | 255404741740 |
| 18 | 1023525137992 |
| 19 | 4097640224516 |
| 20 | 16416968389544 |
| 21 | 65737110052316 |
[56,240,916,3800,14828,60552,239044,967784, 3845148,15493000,61775668,248247480,991807292, 3979719864,15917452772,63817779896,255404741740, 1023525137992,4097640224516,16416968389544, 65737110052316] |