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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 7 |
| 5 | 17 |
| 6 | 49 |
| 7 | 129 |
| 8 | 358 |
| 9 | 970 |
| 10 | 2679 |
| 11 | 7364 |
| 12 | 20414 |
| 13 | 56634 |
| 14 | 157877 |
| 15 | 441084 |
| 16 | 1236496 |
| 17 | 3474672 |
| 18 | 9790403 |
| 19 | 27648486 |
| 20 | 78256907 |
| 21 | 221951037 |
| 22 | 630723367 |
| 23 | 1795576937 |
| 24 | 5120487946 |
| 25 | 14625574662 |
| 26 | 41837955145 |
| 27 | 119851980508 |
| 28 | 343798121799 |
| 29 | 987445317761 |
| 30 | 2839518519233 |
[0,0,1,2,7,17,49,129,358,970,2679,7364,20414, 56634,157877,441084,1236496,3474672,9790403, 27648486,78256907,221951037,630723367,1795576937, 5120487946,14625574662,41837955145,119851980508, 343798121799,987445317761,2839518519233] |