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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 11 |
| 4 | 46 |
| 5 | 167 |
| 6 | 720 |
| 7 | 2915 |
| 8 | 12974 |
| 9 | 55630 |
| 10 | 253309 |
| 11 | 1124806 |
| 12 | 5206427 |
| 13 | 23665135 |
| 14 | 110878569 |
| 15 | 512404479 |
| 16 | 2423117125 |
| 17 | 11336431183 |
| 18 | 53998337998 |
| 19 | 255018739528 |
| 20 | 1221753464002 |
| 21 | 5812862975090 |
| 22 | 27979448361724 |
| 23 | 133913705411633 |
| 24 | 647076980439284 |
| 25 | 3112052367156549 |
| 26 | 15086374420291003 |
| 27 | 72848186260134898 |
[1,1,4,11,46,167,720,2915,12974,55630,253309, 1124806,5206427,23665135,110878569,512404479, 2423117125,11336431183,53998337998,255018739528, 1221753464002,5812862975090,27979448361724, 133913705411633,647076980439284,3112052367156549, 15086374420291003,72848186260134898] |