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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 6 |
| 6 | 16 |
| 7 | 47 |
| 8 | 96 |
| 9 | 206 |
| 10 | 406 |
| 11 | 823 |
| 12 | 1626 |
| 13 | 3244 |
| 14 | 6454 |
| 15 | 12798 |
| 16 | 25715 |
| 17 | 51779 |
| 18 | 103315 |
| 19 | 206649 |
| 20 | 412883 |
| 21 | 825395 |
| 22 | 1650179 |
| 23 | 3299610 |
| 24 | 6600347 |
| 25 | 13201348 |
| 26 | 26403834 |
[0,0,0,1,6,16,47,96,206,406,823,1626,3244,6454, 12798,25715,51779,103315,206649,412883,825395, 1650179,3299610,6600347,13201348,26403834] |