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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 7 |
| 4 | 19 |
| 5 | 40 |
| 6 | 97 |
| 7 | 217 |
| 8 | 508 |
| 9 | 1159 |
| 10 | 2683 |
| 11 | 6160 |
| 12 | 14209 |
| 13 | 32689 |
| 14 | 75316 |
| 15 | 173383 |
| 16 | 399331 |
| 17 | 919480 |
| 18 | 2117473 |
| 19 | 4875913 |
| 20 | 11228332 |
| 21 | 25856071 |
| 22 | 59541067 |
| 23 | 137109280 |
| 24 | 315732481 |
| 25 | 727060321 |
| 26 | 1674257764 |
| 27 | 3855438727 |
| 28 | 8878212019 |
| 29 | 20444528200 |
[1,1,4,7,19,40,97,217,508,1159,2683,6160,14209, 32689,75316,173383,399331,919480,2117473,4875913, 11228332,25856071,59541067,137109280,315732481, 727060321,1674257764,3855438727,8878212019, 20444528200] |