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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 28 |
| 3 | 160 |
| 4 | 636 |
| 5 | 2828 |
| 6 | 11620 |
| 7 | 47388 |
| 8 | 189744 |
| 9 | 762824 |
| 10 | 3056616 |
| 11 | 12220008 |
| 12 | 48892908 |
| 13 | 195589736 |
| 14 | 782409540 |
| 15 | 3129838452 |
[1,4,28,160,636,2828,11620,47388,189744,762824, 3056616,12220008,48892908,195589736,782409540, 3129838452] |