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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 6 |
| 2 | 19 |
| 3 | 56 |
| 4 | 165 |
| 5 | 486 |
| 6 | 1435 |
| 7 | 4248 |
| 8 | 12601 |
| 9 | 37438 |
| 10 | 111367 |
| 11 | 331608 |
| 12 | 988181 |
| 13 | 2946662 |
| 14 | 8791447 |
| 15 | 26241632 |
| 16 | 78359825 |
| 17 | 234069830 |
| 18 | 699404127 |
| 19 | 2090385216 |
| 20 | 6249236653 |
| 21 | 18686125070 |
| 22 | 55884824535 |
| 23 | 167164064984 |
| 24 | 500102988889 |
[1,6,19,56,165,486,1435,4248,12601,37438,111367, 331608,988181,2946662,8791447,26241632,78359825, 234069830,699404127,2090385216,6249236653, 18686125070,55884824535,167164064984,500102988889] |