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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 36 |
| 3 | 432 |
| 4 | 6504 |
| 5 | 118272 |
| 6 | 2525824 |
| 7 | 62011648 |
| 8 | 1721422656 |
| 9 | 53324108032 |
| 10 | 1823657963776 |
| 11 | 68252530738176 |
| 12 | 2774853481548288 |
| 13 | 121780933815238656 |
| 14 | 5738394351838543872 |
| 15 | 288958047466769973248 |
| 16 | 15485497781445500923904 |
[1,4,36,432,6504,118272,2525824,62011648, 1721422656,53324108032,1823657963776, 68252530738176,2774853481548288, 121780933815238656,5738394351838543872, 288958047466769973248,15485497781445500923904] |