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| n | a(n) |
|---|---|
| 1 | 56 |
| 2 | 228 |
| 3 | 932 |
| 4 | 3736 |
| 5 | 15512 |
| 6 | 62040 |
| 7 | 242264 |
| 8 | 969136 |
| 9 | 3985840 |
| 10 | 15943080 |
| 11 | 62096808 |
| 12 | 248388496 |
| 13 | 1021909904 |
| 14 | 4087635248 |
| 15 | 15883066672 |
| 16 | 63532285248 |
| 17 | 261545377088 |
| 18 | 1046181434696 |
| 19 | 4065904153928 |
| 20 | 16263616920064 |
| 21 | 66960253254144 |
[56,228,932,3736,15512,62040,242264,969136, 3985840,15943080,62096808,248388496,1021909904, 4087635248,15883066672,63532285248,261545377088, 1046181434696,4065904153928,16263616920064, 66960253254144] |