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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 20 |
| 2 | 168 |
| 3 | 887 |
| 4 | 3490 |
| 5 | 11196 |
| 6 | 30900 |
| 7 | 75966 |
| 8 | 170379 |
| 9 | 354640 |
| 10 | 693836 |
| 11 | 1288365 |
| 12 | 2287844 |
| 13 | 3908776 |
| 14 | 6456600 |
| 15 | 10352796 |
| 16 | 16167765 |
| 17 | 24660252 |
| 18 | 36824128 |
| 19 | 53943395 |
| 20 | 77656326 |
| 21 | 110029700 |
| 22 | 153644140 |
| 23 | 211691610 |
| 24 | 288086175 |
| 25 | 387589176 |
| 26 | 515950020 |
| 27 | 680063833 |
| 28 | 888147272 |
[1,20,168,887,3490,11196,30900,75966,170379, 354640,693836,1288365,2287844,3908776,6456600, 10352796,16167765,24660252,36824128,53943395, 77656326,110029700,153644140,211691610,288086175, 387589176,515950020,680063833,888147272] |