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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 19 |
| 3 | 173 |
| 4 | 1278 |
| 5 | 8684 |
| 6 | 56772 |
| 7 | 364133 |
| 8 | 2313340 |
| 9 | 14630265 |
| 10 | 92364159 |
| 11 | 583015884 |
| 12 | 3682815128 |
| 13 | 23293263864 |
| 14 | 147556696784 |
| 15 | 936334841109 |
| 16 | 5952158190328 |
| 17 | 37904639744195 |
| 18 | 241809768144945 |
| 19 | 1545250503622245 |
| 20 | 9891049394361030 |
| 21 | 63412712224839600 |
| 22 | 407166098507028432 |
[0,1,19,173,1278,8684,56772,364133,2313340, 14630265,92364159,583015884,3682815128, 23293263864,147556696784,936334841109, 5952158190328,37904639744195,241809768144945, 1545250503622245,9891049394361030, 63412712224839600,407166098507028432] |