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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 1 |
| 7 | 6 |
| 8 | 26 |
| 9 | 100 |
| 10 | 360 |
| 11 | 1246 |
| 12 | 4217 |
| 13 | 14102 |
| 14 | 46861 |
| 15 | 155212 |
| 16 | 513336 |
| 17 | 1697264 |
| 18 | 5614670 |
| 19 | 18594258 |
| 20 | 61671770 |
| 21 | 204907302 |
| 22 | 682110940 |
| 23 | 2275141754 |
[0,0,0,0,0,0,1,6,26,100,360,1246,4217,14102,46861, 155212,513336,1697264,5614670,18594258,61671770, 204907302,682110940,2275141754] |