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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 36 |
| 3 | 156 |
| 4 | 736 |
| 5 | 3132 |
| 6 | 12896 |
| 7 | 53072 |
| 8 | 214556 |
| 9 | 859373 |
| 10 | 3438380 |
| 11 | 13790640 |
| 12 | 55184913 |
| 13 | 220746668 |
| 14 | 883112540 |
| 15 | 3532873541 |
[1,4,36,156,736,3132,12896,53072,214556,859373, 3438380,13790640,55184913,220746668,883112540, 3532873541] |