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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 18 |
| 3 | 134 |
| 4 | 738 |
| 5 | 3529 |
| 6 | 15626 |
| 7 | 66094 |
| 8 | 271592 |
| 9 | 1094970 |
| 10 | 4357916 |
| 11 | 17189832 |
| 12 | 67381030 |
| 13 | 262951065 |
| 14 | 1022931210 |
| 15 | 3970604310 |
| 16 | 15388650480 |
| 17 | 59579400030 |
| 18 | 230518577340 |
| 19 | 891563223876 |
| 20 | 3447681609924 |
| 21 | 13332176226474 |
| 22 | 51561684003588 |
| 23 | 199455373005004 |
| 24 | 771769458006512 |
[0,1,18,134,738,3529,15626,66094,271592,1094970, 4357916,17189832,67381030,262951065,1022931210, 3970604310,15388650480,59579400030,230518577340, 891563223876,3447681609924,13332176226474, 51561684003588,199455373005004,771769458006512] |