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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 18 |
| 4 | 93 |
| 5 | 500 |
| 6 | 2844 |
| 7 | 16621 |
| 8 | 99674 |
| 9 | 608448 |
| 10 | 3770744 |
| 11 | 23653630 |
| 12 | 149925328 |
| 13 | 958737739 |
| 14 | 6178529510 |
| 15 | 40089044100 |
| 16 | 261693178976 |
| 17 | 1717542967251 |
[1,4,18,93,500,2844,16621,99674,608448,3770744, 23653630,149925328,958737739,6178529510, 40089044100,261693178976,1717542967251] |