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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 18 |
| 4 | 47 |
| 5 | 123 |
| 6 | 324 |
| 7 | 849 |
| 8 | 2225 |
| 9 | 5832 |
| 10 | 15284 |
| 11 | 40055 |
| 12 | 104976 |
| 13 | 275114 |
| 14 | 721005 |
| 15 | 1889568 |
| 16 | 4952069 |
| 17 | 12978092 |
| 18 | 34012224 |
| 19 | 89137243 |
| 20 | 233605663 |
| 21 | 612220032 |
| 22 | 1604470380 |
| 23 | 4204901941 |
| 24 | 11019960576 |
| 25 | 28880466844 |
| 26 | 75688234942 |
| 27 | 198359290368 |
| 28 | 519848403193 |
| 29 | 1362388228962 |
[1,2,6,18,47,123,324,849,2225,5832,15284,40055, 104976,275114,721005,1889568,4952069,12978092, 34012224,89137243,233605663,612220032,1604470380, 4204901941,11019960576,28880466844,75688234942, 198359290368,519848403193,1362388228962] |