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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 6 |
| 3 | 46 |
| 4 | 228 |
| 5 | 930 |
| 6 | 3406 |
| 7 | 11682 |
| 8 | 38412 |
| 9 | 122806 |
| 10 | 385182 |
| 11 | 1192254 |
| 12 | 3656452 |
| 13 | 11141178 |
| 14 | 33791934 |
| 15 | 102161962 |
| 16 | 308156748 |
| 17 | 928008846 |
| 18 | 2791497262 |
| 19 | 8390220006 |
| 20 | 25203689700 |
| 21 | 75680274610 |
| 22 | 227185526766 |
| 23 | 681858569586 |
| 24 | 2046204853708 |
[0,0,6,46,228,930,3406,11682,38412,122806,385182, 1192254,3656452,11141178,33791934,102161962, 308156748,928008846,2791497262,8390220006, 25203689700,75680274610,227185526766,681858569586, 2046204853708] |